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Patellar tendinopathyZwerver, Johannes

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Patellar TendinopathyPrevalence, ESWT treatment and Evaluation

J. Zwerver


Zwerver, J

Dissertation University of Groningen, the Netherlands – With ref. – With summary in Dutch

ISBN: 978-90-367-4610-6

© J. Zwerver, Groningen, The Netherlands 2010All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronical or mechanical, including photocopy, recording or any information storage or retrieval system, without the prior written permission of the copyright owner.

Lay-out and cover: Helga de Graaf, Studio Eye Candy, Groningen (www.proefschrift.info)Printed by Ipskamp Drukkers, Enschede

RijkSunivERSiTEiT GRoninGEn


Proefschrift

ter verkrijging van het doctoraat in deMedische Wetenschappen

aan de Rijksuniversiteit Groningen op gezag van de

Rector Magnificus, dr. F. Zwarts,in het openbaar te verdedigen op

woensdag 8 december 2010om 16.15 uur

door

Johannes Zwervergeboren op 3 september 1967

in de Noordoostpolder

Promotor Prof. dr. R.L. Diercks

Copromotores Dr. I. van den Akker-Scheek Dr. F.Hartgens

Beoordelingscommissie Prof. dr. F.J.G. Backx Prof. dr. S.K. Bulstra Prof. dr. K. Peers

Paranimfen Steef Bredeweg Hans de Vries

Contents

Chapter 1 General introduction Chapter 2 Patellar tendinopathy (jumper’s knee): a common and difficult-to-treat sports injury

Chapter 3 Prevalence of patellar tendinopathy in non- elite-athletes Chapter 4 Validity and reliability of the Dutch translation of the VISA-P questionnaire for patellar tendinopathy Chapter 5 Biomechanical analysis of the single-leg decline squat

Chapter 6 Extracorporeal shockwave therapy for patellar tendinopathy: a review of the literature

Chapter 7 The TOPGAME study: effectiveness of extracorporeal shockwave therapy in jumping athletes with patellar tendinopathy. Design of a randomised controlled trial Chapter 8 No effect of extracorporeal shockwave therapy on patellar tendinopathy in jumping athletes during the competitive season: a randomised clinical trial Chapter 9 General discussion Chapter 10 Summary

Appendices A Nederlandse samenvatting B VISA-P questionnaire C Nederlandse VISA-P vragenlijst D Dankwoord E Curriculum Vitae F List of publications G List of (inter)national presentations H Onderwijs en overige activiteiten I Share

9

15

29

41

51

63

79

91

109

127

133141145149155159165173179

Chapter 1

General introduction

General introduction 11

1

Background

The patellar tendon is commonly subject to overuse in sporting activities, especially in sports like basketball and volleyball which require explosive extension of the knee or ec-centric flexion. In 1973 Blazina introduced the term ‘jumper’s knee’ to describe the condi-tion of anterior knee pain in the patellar or quadriceps tendon or at the patellar or tibial attachment of the patellar tendon.1 Nowadays the term patellar tendinopathy is often used in clinical practice for this chronic injury of the patellar tendon, which is clinically characterised by load-dependent pain at the inferior pole of the patella.2,3

Although there have been many advances in the understanding of the histopathology, imaging, and both conservative and surgical outcomes for this condition in the past two decades, successful management of athletes with patellar tendinopathy remains a major challenge for both practitioner and patient.2-6

This is why there is a definite need for studies into prevalence and etiological factors of patellar tendinopathy, feasible evaluation tools and functional tests to rate severity and outcome of interventions, and last but not least randomised controlled trials into the ef-fectiveness of different treatment options.

Aims

The scope of this thesis is to increase our knowledge of patellar tendinopathy in non-elite athletes and the role of extracorporeal shockwave therapy (ESWT) in the management of this condition. The first objective is to describe the prevalence of patellar tendinopathy in non-elite athletes and to find associated risk factors for this overuse injury. The second objective is to develop and study specific (Dutch) evaluation tools for patellar tendinopa-thy. The third objective is to evaluate the effectiveness of ESWT as treatment for patellar tendinopathy.

Outline of the thesis

First, in Chapter 2 an overview is given of the clinical characteristics, etiology, pathophysiol-ogy, diagnostic methods and treatment and rehabilitation options for patellar tendinopathy. Chapter 3 presents the results of a cross-sectional survey into the prevalence of patel-lar tendinopathy among non-elite athletes from seven different sports and some potential risk factors for patellar tendinopathy. The validity and reliability of the Dutch Translation of the VISA-P score, a question-naire that rates symptoms, function and sports participation of athletes with patellar tendinopathy, are presented in Chapter 4. Chapter 5 describes the findings of a biomechanical study that analyses the load on the patellar tendon, knee moment and patellofemoral contact force during the single-leg decline squat, a functional assessment tool for patellar tendinopathy.

12 Chapter 1

In Chapter 6 a review is given of the literature on ESWT for patellar tendinopathy. Chapter 7 describes the design of the TOPGAME study, a prospective multicenter study into the effectiveness of ESWT in active basketball, handball and volleyball play-ers who have patellar tendinopathy with symptoms for less than 12 months. The results of this randomized controlled trial are presented in Chapter 8.Chapter 9 combines the results of the different studies into a general discussion and conclusions are drawn. Practical recommendations and suggestions for further studies are presented.

General introduction 13

1

References1. Blazina ME, Kerlan RK, Jobe FW, Carter VS, Carlson GJ (1973). Jumper’s knee. Orthop Clin

North Am; 4:665-78.

2. Cook JL, Khan KM, Maffulli N, Purdam C (2000). Overuse tendinosis, not tendinitis part 2. Applying the new approach to patellar tendinopathy. Physician and Sportsmedicine; 28:31-+.

3. Khan KM, Cook JL, Bonar F, Harcourt P, Astrom M (1999). Histopathology of common tendinopathies. Update and implications for clinical management. Sports Med; 27:393-408.

4. Coleman BD, Khan KM, Maffulli N, Cook JL, Wark JD (2000). Studies of surgical outcome after patellar tendinopathy: clinical significance of methodological deficiencies and guidelines for future studies. Victorian Institute of Sport Tendon Study Group. Scand J Med Sci Sports; 10:2-11.

5. Cook JL, Khan KM (2001). What is the most appropriate treatment for patellar tendinopathy? Br J Sports Med; 35:291-4.

6. Peers KH, Lysens RJ (2005). Patellar tendinopathy in athletes: current diagnostic and

therapeutic recommendations. Sports Med; 35:71-87.

Chapter 2

Patellar tendinopathy (jumper’s knee):

a common and difficult-to-treat sports injury

J. Zwerver

This chapter is a translated and adapted version of:Patellatendinopathie (‘jumper’s knee’); een veelvoorkomende

en lastig te behandelen sportblessure

Ned Tijdschr Geneeskd. 2008;152:1831-7

16 Chapter 2

Abstract

Patellar tendinopathy is a common and difficult-to-treat overuse injury of the patellar tendon with a very negative impact on the careers of many athletes. It appears to involve a failed healing process in the tendon – not inflammation – and has consequences for the treatment strategy. Rehabilitation programs are based on the principles of load reduction and an eccentric exercise program to improve muscle-tendon function and optimise the kinetic chain. Prolonged rehabilitation is necessary because of slow tendon recovery. Anti-inflammatory treatment is often unsuccessful. Surgery does not guarantee a quick symptom-free return to sport at the original level either. Extracorporeal shockwave therapy, ultrasound-guided sclerosing of new vessels and tendinous and peri-tendinous injections of aprotinin and autologous growth factors seem to be promising new treatment options.

Patellar tendinopathy (jumper’s knee) 17

2

Introduction

Jumper’s knee, also called patellar tendinopathy, is a common condition among both rec-reational and professional athletes,1 and can influence the athlete’s career. In elite basket-ball and volleyball players its prevalence is very high – 32 and 45% respectively.2 It is a chronic injury of the patellar tendon, which is clinically characterised by load-dependent pain at the inferior pole of the patella.1 The high prevalence, the impairment of function and the chronic character of this condition mean that jumper’s knee might have at least as much impact on an athlete’s career as an acute knee injury.2 For some athletes it is even a reason to end their career.3 More than half of athletes with patellar tendinopathy still has some symptoms even 10 years after their career ended.3 General practitioners, physical therapists, sports medicine physicians, sports and reha-bilitation physicians and orthopaedic surgeons frequently see athletes with this typical sports-related knee injury. They use many different treatments, often empirically based, but results are often frustrating for both athlete and doctor or physical therapist.4,5 The poor results can be partly explained by the fact that until recently most treatments were targeted at reducing inflammation in the tendon. In recent years it has been demonstrated that the underlying pathology of patellar tendinopathy, just as in other tendinopathies, is not a tendinitis but rather a failed healing response, tendinosis.6,7 In clinical practice – when no histopathology is available – it is better to speak of patellar tendinopathy. Patel-lar apexitis or patellar tendinitis are also used. This article starts by reviewing the new insights on etiological factors and histopathology of patellar tendinopathy, because they have consequences for the treatment strategy to follow. This is followed by a description of the clinical characteristics and the conservative and surgical treatment of this typical sports injury.

Etiology

The multifactorial etiology of patellar tendinopathy has not yet been completely clari-fied. Men appear to be at a greater risk of getting this condition. Estrogens might protect tendons from getting injured.8 Genetic predisposition seems to be an important factor as well.9

OverloadA disturbed balance between load and loading capacity probably plays an important role. Because this injury is more common among elite than among recreational athletes, a link between training volume and frequency and the prevalence of patellar tendinopathy seems logic.2,10

Reduced loading capacityA reduced loading capacity is also important. If an athlete is less capable of generating or absorbing forces this can result in a wrong jumping and/or landing technique, which gives an increased load on the patellar tendon. Bisseling et al. recently demonstrated

18 Chapter 2

that a stiffer landing strategy, with less motion in knee and ankle, increases the risk for patellar tendinopathy.11 Risk factors associated with this condition are reduced strength of calf, quadriceps and gluteal muscles, inadequate core stability, reduced hamstring and quadriceps flexibility, and hyperpronation of the foot.12,13 Reduced dorsiflexion of the ankle, for example remaining after an ankle distortion which frequently occurs in jump-ing athletes, can play a role.4,14

Pathology

In chronic tendinopathy a failed healing process results in a painful and weakened ten-don, which is then less capable of performing its most important functions, namely ab-sorbing and transducing forces. Repetitive microtrauma caused by overuse give rise to degenerative abnormalities in the tendon like changes in collagen structure and neuro-vascular proliferation.7 There is no inflammatory process. The histopathology is a tendi-nosis, not a tendinitis. Vasculoneural ingrowth might play a role in the concomitant pain in tendinopathies.15

Clinical information

HistoryAthletes with patellar tendinopathy experience pain at the inferior pole of the patella. Pain usually starts insidiously and increases with activities like jumping, sprinting and landing. Symptoms often start after a period of increased training load. In the ini-tial phase symptoms disappear during the warm-up. Athletes tend to keep on going ‘through the pain’ and don’t seek medical help. When they continue to compete at the same level, the pain gradually increases and also remains during sporting activities; eventually, sport performance declines. Finally, there is even pain during daily activities and at rest.To quantify the severity of the patellar tendinopathy during the treatment period one can use the Victorian Institute of Sport Assessment (VISA) score (see Appendix B). For a Dutch translation see Appendix C.16 This questionnaire consisting of eight questions was specifically designed for patellar tendinopathy and evaluates pain, function and sports participation, with a score of 100 reflecting an optimal symptom-free knee. VISA scores of athletes with patellar tendinopathy looking for medical help are around 50–70 points.


2

Physical examinationCircumscript palpation tenderness at the tendon insertion at the inferior pole of the pa-tella is the most characteristic finding during physical examination. The patellar tendon can be thickened. A common finding is atrophy of the quadriceps muscle, especially the M. vastus medialis.As mentioned before, it is important to evaluate potential etiological factors like reduced muscle-tendon function, inappropriate core stability and limited ranges of motion of sev-eral joints. The single leg decline squat is a functional test that loads the patellar tendon and can provoke pain. In this test the athlete, standing on one leg on a decline board at an angle of approximately 25 degrees, gradually flexes the knee (figure 2.1).17 The test can be used to substantiate the diagnosis, but there is no gold standard.

Imaging techniques Although MRI and ultrasound can increase the likelihood of a diagnosis of patellar tendi-nopathy, their value is limited (figures. 2.2 and 2.3).18-22 Patellar tendons of asymptomatic athletes often show sonographic abnormalities, and symptoms and abnormalities can vary during the sports season.23,24 The prognostic and follow-up value of MRI and ultra-sound are also limited because of the poor correlation between clinical symptoms and imaging abnormalities in the tendon.21,25 There may be a correlation between neovascu-larisation (figure 2.3b) on Doppler ultrasound and experienced pain.26,27

Figure 2.1 ‘Single leg decline squat’ test: pain-provoking test to increase the likelihood of patellar tendinopathy.

20 Chapter 2

Figure 2.2. Ultrasound characteristics of patellar tendinopathy: (a) thickened tendon with hypo-echogenic zones and calcifications; (b) colour-Doppler appearance of neovascularisation in the tendon.

femur

tibia

patellaFigure 2.3. MRI of patellar tendinopathy, with increased signal intensity in the proximal part of the tendon; (b) in MRI using a fat-suppression technique.

femur

tibia

patella


2

Conservative treatment

Several, mostly not evidence-based treatment options are used in the management of patellar tendinopathy.4,5 With the current understanding that the underlying pathology in tendinopathies is a tendinosis and not a tendinitis, one should reconsider the treatment strategy. A treatment program for patellar tendinopathy should aim mainly at restor-ing the balance between load and loading capacity and stimulating tendon regeneration rather than reducing the inflammatory process.28

Explanation Athletes with patellar tendinopathy need to get an explanation about the overuse and chronic character of their injury, and should be informed about the fact that a rehabilita-tion program often takes more than three months to achieve full recovery.

Pain reduction Reduction of tendon load can reduce the pain to a tolerable level for the athlete. This does not mean that athletes should completely refrain from tendon-loading activities. Complete rest or even stronger complete immobilisation leads to further weakening of the muscle-tendon unit. It is better to load the tendon very carefully, thereby enabling the athlete to perform pain-free daily activities, participate in a rehabilitation program and adjust sporting activities. Ice packs, taping and bracing (patellar strap) and electrophysical mo-dalities sometimes give some short-term pain relief, but did not evidence a pain-reducing or regenerative effect at longer follow-up.

Exercise therapy to increase loading capacity If strength and endurance of calf, quadriceps and gluteal muscles are weakened one should prescribe strength-training exercises to improve muscle performance. Core stabil-ity should also be optimised. Limitations in joint movements and other causal factors should be corrected. Sport-specific exercises should be included in the final part of the rehabilitation program.

Eccentric exercises Eccentric, slightly painful exercises like the aforementioned single-leg decline squat ap-pear to be effective in the treatment of tendinopathies.6,29-31 During an eccentric contrac-tion the muscle-tendon unit becomes elongated while the muscle contracts, in contrast to isometric and concentric contractions, in which the length respectively stays the same or becomes shorter. For example, during the single-leg decline squat the quadriceps muscle contracts while the patellar tendon-quadriceps unit elongates. Using this eccentric treat-ment strategy VISA scores improved by about 30 points.A practical recommendation for athletes is to perform single-leg decline squats on the in-jured leg once or twice a day, in three series of 15 repetitions for a period of 12 weeks. The precise working mechanism is still unclear but it is likely that these exercises stimulate regeneration in the tendon. The old adage that exercise therapy should be painless is thus open to debate. Some pain during exercise therapy can lead to good treatment results when pain settles within 24 hours and does not increase day by day.32

22 Chapter 2

Extracorporeal shockwave therapyExtracorporeal shockwave therapy seems to be an appropriate additional treatment. Some randomised placebo-controlled studies demonstrate the effectiveness of ESWT on pain and function in patellar tendinopathy.5,33 After ESWT treatment, athletes showed 30 to 40 points higher VISA scores than the control group. The beneficial effect of ESWT might be the result of an analgetic process, destruction of calcifications and stimulation of regeneration processes in the tendon. Unlike ESWT, low-intensity pulsed ultrasound showed no additional benefit over an eccentric training program.34

Anti-inflammatory medication Treatments aimed at reducing inflammation, like the commonly used NSAIDs and injec-tions with corticosteroids, seem to be illogic for degenerative tendons without inflamma-tion. At best, they give short-term pain relief, however their effectiveness in the long run has not been demonstrated. Because of their pain-reducing effect they can mask under-lying problems, resulting in even more extensive tendon abnormalities. Injections with corticosteroids have been controversial in recent decades since they influence collagen synthesis negatively and reduce tendon strength.

Ultrasound guided sclerotherapy An interesting new treatment method is ultrasound-guided sclerosis of the neovessels in the tendon with polidocanol, a well-known sclerosant to treat varices. It is presumed that tendinopathy pain is caused by neurovascular ingrowth in the tendon.35 The effectiveness of this treatment method was recently demonstrated in a randomised clinical trial.36

Figure 2.4. Different types of

muscle contractions:

(a) isometric contraction;

(b) concentric contraction;

(c) eccentric contraction (arrows

indicate direction of movement).


2

Other injection techniques Tendinous and peritendinous injections with aprotinin, a protease inhibitor, or with autol-ogous blood or platelet-rich plasma and growth factors seem to be successful, but further research into the effectiveness of these treatments is necessary.37,38

Surgical treatment

Surgical treatment can be an option when despite a comprehensive and extensive reha-bilitation program conservative treatment fails. Several surgical procedures have been described. Success rates in the literature vary between 60 and 100% and are inversely correlated with methodological quality.39 A recent clinical trial demonstrated that open tenotomy has no advantage over eccentric training.40 Surgery does not guarantee a quick, symptom-free return to sports at the original level. Also, after surgery a prolonged reha-bilitation period according the aforementioned guidelines is necessary.

Conclusion

Patellar tendinopathy is a common overuse injury of the patellar tendon with a very negative impact on the career of an athlete. Up to now no single treatment exists that guarantees a quick and symptom-free return to the original sports level. Therefore, a pro-longed rehabilitation program to restore the balance between load and loading capacity and to promote regeneration of the tendon is the best treatment.

24 Chapter 2


North Am; 4:665-78.

2. Lian OB, Engebretsen L, Bahr R (2005). Prevalence of jumper’s knee among elite athletes from different sports: a cross-sectional study. Am J Sports Med; 33:561-7.

3. Kettunen JA, Kvist M, Alanen E, Kujala UM (2002). Long-term prognosis for jumper’s knee in male athletes. A prospective follow-up study. Am J Sports Med; 30:689-92.


5. Peers KH, Lysens RJ (2005). Patellar tendinopathy in athletes: current diagnostic and therapeutic recommendations. Sports Med; 35:71-87.

6. van Linschoten R, den Hoed PT, de Jongh AC (2007). [Guideline ‘Chronic Achilles tendinopathy, in particular tendinosis, in sportsmen/sportswomen’]. Ned Tijdschr Geneeskd; 151:2319-24.


8. Cook JL, Bass SL, Black JE (2007). Hormone therapy is associated with smaller Achilles tendon diameter in active post-menopausal women. Scand J Med Sci Sports; 17:128-32.

9. Mokone GG, Gajjar M, September AV, Schwellnus MP, Greenberg J, Noakes TD, Collins M (2005). The guanine-thymine dinucleotide repeat polymorphism within the tenascin-C gene is associated with achilles tendon injuries. Am J Sports Med; 33:1016-21.

10. Ferretti A (1986). Epidemiology of jumper’s knee. Sports Med; 3:289-95.

11. Bisseling RW, Hof AL, Bredeweg SW, Zwerver J, Mulder T (2007). Relationship between landing strategy and patellar tendinopathy in volleyball. Br J Sports Med; 41:e8.

12. Gaida JE, Cook JL, Bass SL, Austen S, Kiss ZS (2004). Are unilateral and bilateral patellar tendinopathy distinguished by differences in anthropometry, body composition, or muscle strength in elite female basketball players? Br J Sports Med; 38:581-5.

13. Witvrouw E, Bellemans J, Lysens R, Danneels L, Cambier D (2001). Intrinsic risk factors for the development of patellar tendinitis in an athletic population. A two-year prospective study. Am J Sports Med; 29:190-5.

14. Malliaras P, Cook JL, Kent P (2006). Reduced ankle dorsiflexion range may increase the risk of patellar tendon injury among volleyball players. J Sci Med Sport; 9:304-9.

15. Alfredson H (2005). The chronic painful Achilles and patellar tendon: research on basic biology and treatment. Scand J Med Sci Sports; 15:252-9.

16. Visentini PJ, Khan KM, Cook JL, Kiss ZS, Harcourt PR, Wark JD (1998). The VISA score: an index of severity of symptoms in patients with jumper’s knee (patellar tendinosis). Victorian Institute of Sport Tendon Study Group. J Sci Med Sport; 1:22-8.


2

17. Zwerver J, Bredeweg SW, Hof AL (2007). Biomechanical analysis of the single-leg decline squat. Br J Sports Med; 41:264-8.

18. Cook JL, Kiss ZS, Khan KM (1999). Patellar tendinitis: the significance of magnetic resonance imaging findings. Am J Sports Med; 27:831.

19. Cook JL, Khan KM, Kiss ZS, Purdam CR, Griffiths L (2000). Prospective imaging study of asymptomatic patellar tendinopathy in elite junior basketball players. J Ultrasound Med; 19:473-9.

20. Cook JL, Khan KM, Kiss ZS, Coleman BD, Griffiths L (2001). Asymptomatic hypoechoic regions on patellar tendon ultrasound: A 4-year clinical and ultrasound followup of 46 tendons. Scand J Med Sci Sports; 11:321-7.

21. Khan K, Kannus P (2000). Use of imaging data for predicting clinical outcome. Br J Sports Med; 34:73.

22. Warden SJ, Kiss ZS, Malara FA, Ooi AB, Cook JL, Crossley KM (2007). Comparative accuracy of magnetic resonance imaging and ultrasonography in confirming clinically diagnosed patellar tendinopathy. Am J Sports Med; 35:427-36.

23. Malliaras P, Cook J, Ptasznik R, Thomas S (2006). Prospective study of change in patellar tendon abnormality on imaging and pain over a volleyball season. Br J Sports Med; 40:272-4.

24. Malliaras P, Cook J (2006). Patellar tendons with normal imaging and pain: change in imaging and pain status over a volleyball season. Clin J Sport Med; 16:388-91.

25. Khan KM, Visentini PJ, Kiss ZS, Desmond PM, Coleman BD, Cook JL, Tress BM, Wark JD, Forster BB (1999). Correlation of ultrasound and magnetic resonance imaging with clinical outcome after patellar tenotomy: prospective and retrospective studies. Victorian Institute of Sport Tendon Study Group. Clin J Sport Med; 9:129-37.

26. Cook JL, Malliaras P, De Luca J, Ptasznik R, Morris ME, Goldie P (2004). Neovascularization and pain in abnormal patellar tendons of active jumping athletes. Clin J Sport Med; 14:296-9.

27. Cook JL, Malliaras P, De Luca J, Ptasznik R, Morris M (2005). Vascularity and pain in the patellar tendon of adult jumping athletes: a 5 month longitudinal study. Br J Sports Med; 39:458-61.

28. Kountouris A, Cook J (2007). Rehabilitation of Achilles and patellar tendinopathies. Best Pract Res Clin Rheumatol; 21:295-316.

29. Jonsson P, Alfredson H (2005). Superior results with eccentric compared to concentric quadriceps training in patients with jumper’s knee: a prospective randomised study. Br J Sports Med; 39:847-50.

30. Young MA, Cook JL, Purdam CR, Kiss ZS, Alfredson H (2005). Eccentric decline squat protocol offers superior results at 12 months compared with traditional eccentric protocol for patellar tendinopathy in volleyball players. Br J Sports Med; 39:102-5.

31. Purdam CR, Jonsson P, Alfredson H, Lorentzon R, Cook JL, Khan KM (2004). A pilot study of the eccentric decline squat in the management of painful chronic patellar tendinopathy. Br J Sports Med; 38:395-7.

26 Chapter 2

32. Silbernagel KG, Thomee R, Eriksson BI, Karlsson J (2007). Continued sports activity, using a pain-monitoring model, during rehabilitation in patients with Achilles tendinopathy: a randomized controlled study. Am J Sports Med; 35:897-906.

33. Wang CJ, Ko JY, Chan YS, Weng LH, Hsu SL (2007). Extracorporeal shockwave for chronic patellar tendinopathy. Am J Sports Med; 35:972-8.

34. Warden SJ, Metcalf BR, Kiss ZS, Cook JL, Purdam CR, Bennell KL, Crossley KM (2008). Low-intensity pulsed ultrasound for chronic patellar tendinopathy: a randomized, double-blind, placebo-controlled trial. Rheumatology (Oxford); 47:467-71.

35. Ohberg L, Alfredson H (2002). Ultrasound guided sclerosis of neovessels in painful chronic Achilles tendinosis: pilot study of a new treatment. Br J Sports Med; 36:173-5.

36. Hoksrud A, Ohberg L, Alfredson H, Bahr R (2006). Ultrasound-guided sclerosis of neovessels in painful chronic patellar tendinopathy: a randomized controlled trial. Am J Sports Med; 34:1738-46.

37. James SL, Ali K, Pocock C, Robertson C, Walter J, Bell J, Connell D (2007). Ultrasound guided dry needling and autologous blood injection for patellar tendinosis. Br J Sports Med; 41:518-21.

38. Capasso G, Testa V, Maffuli N, Bifulco G (1997). Aprotinin, corticosteroids and normosaline in the management of patellar tendinopathy in athletes: a prospective randomised study. Sports Exerc Inj; 3:111-5.

39. Coleman BD, Khan KM, Kiss ZS, Bartlett J, Young DA, Wark JD (2000). Open and arthroscopic patellar tenotomy for chronic patellar tendinopathy. A retrospective outcome study. Victorian Institute of Sport Tendon Study Group. Am J Sports Med; 28:183-90.

40. Bahr R, Fossan B, Loken S, Engebretsen L (2006). Surgical treatment compared with eccentric training for patellar tendinopathy (Jumper’s Knee). A randomized, controlled trial. J Bone Joint Surg Am; 88:1689-98.

Chapter 3

Prevalence of patellar tendinopathy in

non-elite-athletes

J. Zwerver S.W. Bredeweg

I. van den Akker-Scheek

Submitted

30 Chapter 3

Abstract

Background: The prevalence of jumper’s knee among non-elite athletes from different sports is unknown.

Aim: To determine the prevalence of jumper’s knee in non-elite athletes from different sports and to determine potential risk factors for jumper’s knee.

Study design: Cross-sectional survey.

Methods: We interviewed 891 male and female non-elite athletes from seven popular sports in the Netherlands: basketball, volleyball, handball, korfball, soccer, field hockey and athletics. Using a specially developed questionnaire information was obtained about individual characteristics (age, height and weight), training background, previous and actual knee problems and the VI-SA-P score.

Results: The overall prevalence of current jumper’s knee was 8.5% (78 out of 891 athletes), showing a significant difference between sports with different loading characteristics and playing surfaces. Prevalence was highest among volleyball players (14.4%) and lowest among soccer players (2.5%); it was sig-nificantly higher among male athletes (51 out of 502, 10.2%) than female ath-letes (25 out of 389, 6.4%) (χ2=3.91, p=0.048). Mean duration of symptoms was 18.9 months (SD 21.6; range 2.0–59.8). The mean VISA-P score of the athletes with jumper’s knee was 71.4 (SD 13.8). Age, height and weight were signifi-cantly different between athletes with jumper’s knee and those without.

Conclusions: Prevalence of jumper’s knee is high among non-elite athletes and varies between 2.5% and 14.4% for different sports. Jumper’s knee is al-most twice as common among male non-elite athletes compared to female ath-letes. Different sport-specific loading characteristics of the knee extensor appa-ratus, playing surface, age, height and weight seem to be risk factors associated with patellar tendinopathy.

Prevalence in non-elite athletes 31

3

Introduction

Jumper’s knee is characterised by activity-related anterior knee pain and focal patellar or quadriceps tendon tenderness.1 Jumper’s knee often causes prolonged morbidity and disability, and many athletes have to end their career because of this overuse injury.2,3 The etiology and underlying pathophysiology have not been completely elucidated so far. Repetitive microtrauma due to overuse causes (neuro)inflammatory and degenera-tive changes in the tendon, which finally fails to heal.4,5

Prevention seems to be of the utmost importance, since treatment is often hampered by a lack of scientific evidence directing the management of this condition. Several treatments have been described but which is the most appropriate treatment approach remains unclear.6,7 In order to develop preventive strategies for this condition, more insight into its magnitude and etiology is necessary.8,9

Some research has been conducted into the prevalence of jumper’s knee, revealing an overall prevalence of 14% among elite athletes.3 Among elite volleyball and basket-ball players a prevalence of 45% and 32% respectively has been reported.3 Little is known about the prevalence of jumper’s knee in non-elite, recreational athletes though. Hence the aim of the present study was to estimate the prevalence of jumper’s knee in non-elite athletes from different sports and to determine potential risk factors for this condition.

Methods

Study designWe performed a cross-sectional evaluation among male and female athletes from 7 differ-ent popular sports in the northern Netherlands: basketball, volleyball, handball, korfball, soccer, field hockey and athletics. Teams and athletes were randomly chosen and asked to participate in this study. Only athletes who participated in the local or regional competi-tion or recreational athletes were included. Professional players or athletes at the national elite level were excluded. After permission from the coaches the interviews were sched-uled right after a training session during the competitive season. All athletes who were present at the training agreed to fill out a specially developed questionnaire. The study was conducted according to the regulations of the Medical Ethical Committee at the Uni-versity Medical Center Groningen, participation was voluntary, and it was explained that completing the questionnaire would be seen as consent to participate.

QuestionnaireEach athlete filled out a specially designed questionnaire under the supervision of a trained interviewer. In the first part information was obtained about gender, age, height and weight. The second part included questions regarding sports participation: years of participation and number of hours per week. The third part was a structured medical history for previous and current knee problems. Each athlete went through this stan-dardised interview, and the information requested included:

32 Chapter 3

past knee injuries or complaints, previous diagnosis and treatment if a physician 1. or physical therapist was consulted;current knee problems: side of symptoms, diagnosis and treatment if a physician 2. or physical therapist was consulted, localisation of pain in a diagram of the knee, duration of symptoms, acute or gradual onset, symptoms during or after athletic activities.

The diagnosis of jumper’s knee was deducted from several answers in the questionnaire combining: 1) a typical history of gradually developed activity-related anterior knee pain; and 2) a circumscript most painful spot just – pointed out in a diagram of the knee – at the upper or lower pole of the patella, in the patellar tendon or at its tibial insertion; and/or 3) previous diagnosis of this condition by a physician or physical therapist. To assess severity, those athletes with current symptoms suggestive of jumper’s knee also filled out the Dutch version of the VISA-P questionnaire (See Appendix C).10,11 This questionnaire consists of eight questions, six of them rating pain during activities of daily living and simple tests of function on a visual analogue scale ranging from 0 to 10 points, with 10 representing optimal health. Two questions concern the ability to partici-pate in sporting activities. The maximum VISA score for an asymptomatic athlete is 100 points. The translated version of the VISA-P questionnaire is equivalent to its original version, has satisfactory test-retest reliability and is a valid score to evaluate symptoms, knee function and ability to play sports in Dutch athletes with patellar tendinopathy.

Data analysisThe prevalence of jumper’s knee was calculated for each sport separately and expressed in a percentage. A chi-square test was used to determine whether the prevalence differed between the 7 sports and between males and females. Descriptive statistics were used for the characteristics of the athletes per sport, and an ANOVA (with posthoc tests with Bonferroni correction) for a continuous variable or a chi-square test for a dichotomous variable was used to determine whether there were differences between the sports. Mean (±SD) VISA-P score and mean (±SD) duration of symptoms were calculated in athletes with jumper’s knee. Characteristics of athletes with and without jumper’s knee were com-pared using Student’s t-tests. A p-value < 0.05 was considered statistically significant. All analyses were performed using SPSS 16.0.

Results

Of a total 891 non-elite athletes, 76 currently had a jumper’s knee, which is an over-all prevalence of 8.5%. The prevalence differed between the 7 different kind of sports (χ2=21.5, p=0.001), and was highest in volleyball players (14.4%) and lowest in soccer players (2.5%) (Table 3.1). The prevalence was significantly higher in male athletes (51 out of 502, 10.2%) than in female athletes (25 out of 389, 6.4%) (χ2=3.91, p=0.048).There was a significant difference in age between sports; hockey players were older than players of all other sports, except for soccer. There was also a significant difference in BMI; athletics had lower BMI compared to all other athletes, while handball players had


3

higher BMI compared to all other athletes except for hockey and soccer players. The male/female distribution was significantly different between sports. There was also a difference in height, weight, current number of training and match hours, and total years playing sports.The mean VISA-P score of the athletes with jumper’s knee was 71.4 (SD 13.8). Their VISA-P score was not significantly different between sports (ANOVA, p=0.94). Mean duration of symptoms was 18.9 months (SD 21.6; range 2.0–59.8). Age, height and weight were sig-nificantly different between athletes with jumper’s knee and those without. Athletes with jumper’s knee were significantly younger (22.8±3.1 years vs. 24.1±4.8 years; p=0.002), were taller (185±10.3 cm vs. 181±9.8 cm; p=0.001) and weighed more (77.4±11.1 kg vs. 73.6±11.6 kg; p=0.006). BMI, total years playing sports and current number of training and match hours did not differ between athletes with and without jumper’s knee.

Table 3.1. Prevalence of jumper’s knee in 7 different sports and athletes characteristics.

Basketball Volleyball Handball Korfball SoccerField

hockeyAthletics

N 127 153 105 145 118 98 145

Prevalence JK 11.8% 14.4% 13.3% 4.8% 2.5% 5.1% 6.9%

Men 89 (70.1%) 76 (49.7%) 45 (42.9%) 76 (52.4%) 92 (78%) 49 (50.0%) 75 (51.7%)

Age (years) 23.6 (4.3) 22.9 (2.7) 23.8 (5.2) 23.2 (4.2) 24.7 (5.1) 26.6 (6.2) 24.0 (4.5)

BMI (kg/m2) 22.5 (2.2) 22.2 (2.0) 23.5 (2.3) 22.5 (2.2) 23.0 (2.5) 22.7 (2.7) 21.1 (2.0)

Height (cm) 186 (9.6) 182 (10.1) 179 (9.0) 180 (10.0) 181 (8.1) 179 (9.9) 178 (9.8)

Weight (kg) 78.4 (11.1) 74.2 (10.9) 76.1 (11.9) 73.4 (11.2) 75.9 (11.0) 73.3 (12.4) 67.3 (10.1)

Sport history (years) 9.3 (5.1) 9.9 (4.8) 13.8 (7.2) 15.1 (4.9) 16.5 (5.6) 15.5 (6.9) 8.7 (6.0)

Hours sporting (/week) 4.6 (1.8) 5.0 (2.2) 5.7 (4.1) 4.0 (1.3) 4.7 (1.7) 4.2 (2.1) 5.7 (3.2)

34 Chapter 3

Discussion

This cross-sectional survey among non-elite, recreational athletes from 7 different sports showed that the overall prevalence of jumper’s knee varied between 2.5% (soccer) and 14.4% (volleyball). The overall prevalence in the sports included in this survey was 8.5%. Athletes with jumper’s knee reported a mean VISA-P score of 71.4 (SD 13.8) and had symptoms for 18.9 months (SD 21.6; range 2.0–59.8). No differences were found between the sports with regard to severity (VISA-P) or duration of jumper’s knee symptoms. Age, height and weight were significantly different between athletes with jumper’s knee and those without.This the first study to describe the prevalence of jumper’s knee in non-elite athletes of different sports. The study’s reported prevalence of 8.5% indicates that jumper’s knee is also a common problem in this population and not only prevalent among elite athletes, albeit prevalence among the latter is higher. Lian et al. showed a prevalence of current jumper’s knee in male athletes of around 45% in volleyball, 32% in basketball, 23% in athletics, 15% in handball and 12% in soccer, whereas in our survey a lower prevalence of 14%, 12%, 7%, 13% and 3% respectively was found in these sports for both male and female athletes.3 Since jumper’s knee is considered to be an overuse injury that affects men more than women, the inclusion of female athletes in our study explains part of the difference in prevalence found between elite and non-elite athletes. In line with previous studies, we also found a significantly higher prevalence in male athletes (51 out of 502, 10.2%) than in female athletes (25 out of 389, 6.4%).3,12 It remains unclear why jumper’s knee affects more men than women but some hypotheses have been postulated. One explanation could be that women have less quadriceps strength and inferior jumping capacity, so the pa-tellar tendon is exposed to lower forces.13 Estrogens may play a protective role against tendinopathies,12 although other studies have shown that estrogen inhibits exercise-in-duced collagen synthesis in the human tendon and leads to a lower rate of tendon tissue repair.14,15 In any event, the difference between the prevalence of jumper’s knee found in elite athletes and non-elite athletes cannot solely be explained by the fact that our study also included female athletes.It is reasonable to assume that the number of training hours also plays a role. The elite athletes included in the study of Lian et al. practiced more than 12 hours/week, whereas in our study total number of weekly sporting hours was only 4 to 5. Ferretti already described a linear relationship between training volume and prevalence of jumper’s knee in volleyball players.16

The prevalence of jumper’s knee was highest in basketball, volleyball and handball, all indoor sports characterised by high demands on speed and power for the leg extensors. There seems to be an association between sport-specific knee-loading characteristics, playing surface and prevalence of jumper’s knee. Korfball, a typical Dutch sport also with many jumping, cutting and sprinting activities, had a much lower prevalence, which might be partly explained by the fact that most of the time it is played outdoors on a softer natural grass pitch. Field hockey, not a typical jumping sport but played on hard artificial turf, showed a higher prevalence than soccer. In a study among elite beach vol-leyball players, who jump and land in soft sand, a prevalence of 9% has been reported,


3

which is much lower than for indoor volleyball players.17 It therefore seems plausible that the higher the mechanical overload on the tendon the greater the risk for developing a jumper’s knee. Studies are needed to elucidate the exact underlying pathophysiological mechanism of patellar tendinopathy caused by this repetitive overloading of the ten-don.Age, height and weight were found to be significantly different between non-elite athletes with and without a jumper’s knee. This result is in contrast to many other studies. We have recently reviewed the literature on etiological factors associated with patellar tendi-nopathy and found strong-to-moderate evidence that age,3,12,16,18-20 weight in females12,18,20-23 and height12,18-23 are not associated with patellar tendinopathy. Most of these studies how-ever were performed on high-level athletes. There may be different risk factors for elite and non-elite athletes; more research on the latter group is thus needed.When interpreting our results some methodological issues must be considered. The di-agnosis of jumper’s knee was deducted from the questionnaire and was based on the typical history, location of tenderness in a pain map and/or a previous diagnosis by an independent practitioner. No clinical examination by a (sports medicine) physician was performed and no MR or ultrasound imaging was done. This might have influenced the results of our study. However, several studies have used self-administered pain maps for the inclusion of subjects with jumper’s knee.24,25 The location of knee pain as indicated on a self-administered pain map corresponds very well with the actual pain location.26 Furthermore, the diagnostic method with a self-administered pain map appeared to be quite reliable in a previous study.27 Out of a group of 268 athletes who based on the questionnaire criteria were classified as having jumper’s knee, 45 athletes were invited to participate in an intervention study. Jumper’s knee was diagnosed by an experienced sports medicine physician in 44 of the 45 subjects, demonstrating that the number of false-positives was very low. As for the lack of MR and ultrasound imaging, it is also well-known that there is limited correlation between clinical symptoms and ultrasound or MR imaging.28,29 Pain can exist without detectable tendon changes, but athletes can also have imaging abnormalities of their tendon without symptoms of jumper’s knee. MR and ultrasound imaging thus increase the likelihood of a clinical diagnosis being made but are not the gold standard. Thus we believe that the method used in this study is a valid one to diagnose jumper’s knee in large cohorts.Another limitation is that only those athletes who were able to practice filled out the ques-tionnaire, since the interviews were held directly after the training sessions. Anecdotal evidence shows that at least 3 athletes did not participate in the practice session because of a jumper’s knee problem and that 2 stopped for the same reason. Hence the prevalence found in this study might even be an underestimation of the problem.In the sequence of sports injury prevention research it is therefore important to realize that jumper’s knee is a common, often chronic condition among recreational athletes too.8,9 Although it is not a time-loss injury, it can negatively influence an athlete’s career. Many athletes with jumper’s knee keep on playing sports, and based on VISA-P scores of 71 and symptoms duration of more than one-and-a-half years it can be concluded that their athletic performance is chronically hampered by their knee problem. This phenomenon of “no injuries, but plenty of pain” has recently been described by Bahr.30 The next step is more research into etiological factors and injury mechanisms in order to determine po-

36 Chapter 3

tential strategies that can reduce the load on the patellar tendon. Only then can preventive measures be developed and introduced which reduce the risk of sustaining this common and bothersome injury.

Conclusion

Prevalence of jumper’s knee is high among non-elite athletes and varies between 14.4% and 2.5% for different sports. Jumper’s knee is almost twice as common among male non-elite athletes than among female athletes. Different sport-specific loading characteristics of the knee extensor apparatus and playing surface seem to be risk factors associated with patellar tendinopathy.

AcknowledgementWe would like to thank Anouck Bletterman, Frank Buist, Martijn Doorn, Wendy van Faassen, Maaike

Rozeman, Rene Scholten and Hester Verburg for their help in collecting the data and interviewing the

athletes.


3


North Am; 4:665-78.



4. Abate M, Gravare Silbernagel K, Siljeholm C, Di Iorio A, De Amicis D, Salini V, Werner S, Paganelli R (2009). Pathogenesis of tendinopathies: inflammation or degeneration? Arthritis Res Ther; 11:235.




8. Finch C (2006). A new framework for research leading to sports injury prevention. J Sci Med Sport; 9:3-9.

9. van Mechelen W, Hlobil H, Kemper HC (1992). Incidence, severity, aetiology and prevention of sports injuries. A review of concepts. Sports Med; 14:82-99.


11. Zwerver J, Kramer T, Akker-Scheek I (2009). Validity and reliability of the Dutch translation of the VISA-P questionnaire for patellar tendinopathy. BMC Musculoskelet Disord; 10:102.

12. Gaida JE, Cook JL, Bass SL, Austen S, Kiss ZS (2004). Are unilateral and bilateral patellar tendinopathy distinguished by differences in anthropometry, body composition, or muscle strength in elite female basketball players? Br J Sports Med; 38:581-5.

13. McNitt-Gray JL (2000). Musculoskeletal loading during landing. In: Zatziorsky V, editor. Biomechanics in Sport.Oxford, England: Blackwell Science.

14. Hansen M, Miller BF, Holm L, Doessing S, Petersen SG, Skovgaard D, Frystyk J, Flyvbjerg A, Koskinen S, Pingel J, Kjaer M, Langberg H (2009). Effect of administration of oral contraceptives in vivo on collagen synthesis in tendon and muscle connective tissue in young women. J Appl Physiol; 106:1435-43.

15. Miller BF, Hansen M, Olesen JL, Schwarz P, Babraj JA, Smith K, Rennie MJ, Kjaer M (2007). Tendon collagen synthesis at rest and after exercise in women. J Appl Physiol; 102:541-6.

16. Ferretti A (1986). Epidemiology of jumper’s knee. Sports Med; 3:289-95.

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17. Bahr R, Reeser JC (2003). Injuries among world-class professional beach volleyball players. The Federation Internationale de Volleyball beach volleyball injury study. Am J Sports Med; 31:119-25.

18. Crossley KM, Thancanamootoo K, Metcalf BR, Cook JL, Purdam CR, Warden SJ (2007). Clinical features of patellar tendinopathy and their implications for rehabilitation. J Orthop Res; 25:1164-75.

19. Lian O, Engebretsen L, Ovrebo RV, Bahr R (1996). Characteristics of the leg extensors in male volleyball players with jumper’s knee. Am J Sports Med; 24:380-5.

20. Witvrouw E, Bellemans J, Lysens R, Danneels L, Cambier D (2001). Intrinsic risk factors for the development of patellar tendinitis in an athletic population. A two-year prospective study. Am J Sports Med; 29:190-5.

21. Cook JL, Kiss ZS, Khan KM, Purdam CR, Webster KE (2004). Anthropometry, physical performance, and ultrasound patellar tendon abnormality in elite junior basketball players: a cross-sectional study. Br J Sports Med; 38:206-9.

22. Kujala UM, Osterman K, Kvist M, Aalto T, Friberg O (1986). Factors predisposing to patellar chondropathy and patellar apicitis in athletes. Int Orthop; 10:195-200.

23. Malliaras P, Cook JL, Kent PM (2007). Anthropometric risk factors for patellar tendon injury among volleyball players. Br J Sports Med; 41:259-63.

24. Cook JL, Khan KM, Kiss ZS, Griffiths L (2000). Patellar tendinopathy in junior basketball players: a controlled clinical and ultrasonographic study of 268 patellar tendons in players aged 14-18 years. Scand J Med Sci Sports; 10:216-20.

25. Cook JL, Khan KM, Kiss ZS, Purdam CR, Griffiths L (2001). Reproducibility and clinical utility of tendon palpation to detect patellar tendinopathy in young basketball players. Victorian Institute of Sport tendon study group. Br J Sports Med; 35:65-9.

26. Post WR, Fulkerson J (1994). Knee pain diagrams: correlation with physical examination findings in patients with anterior knee pain. Arthroscopy; 10:618-23.

27. Zwerver J, Verhagen E, Hartgens F, Akker-Scheek I, Diercks RL (2010). The TOPGAME-study: effectiveness of extracorporeal shockwave therapy in jumping athletes with patellar tendinopathy. Design of a randomised controlled trial. BMC Musculoskelet Disord; 11:28.


29. Shalaby M, Almekinders LC (1999). Patellar tendinitis: the significance of magnetic resonance imaging findings. Am J Sports Med; 27:345-9.

30. Bahr R (2009). No injuries, but plenty of pain? On the methodology for recording overuse symptoms in sports. Br J Sports Med; 43:966-72.

Chapter 4

Validity and reliability of the Dutch translation of

the VISA-P questionnairefor patellar tendinopathy

J. Zwerver T. Kramer


BMC Musculoskelet Disord. 2009 Aug 11;10(1):102

42 Chapter 4

Abstract

Background: The VISA-P questionnaire evaluates severity of symptoms, knee function and ability to play sports in athletes with patellar tendinopa-thy. This English-language self-administered brief patient outcome score was developed in Australia to monitor rehabilitation and to evaluate outcome of clinical studies.

Aim: To translate the VISA-P questionnaire into Dutch and to study the reli-ability and validity of the Dutch version.

Methods: The questionnaire was translated into Dutch according to interna-tionally recommended guidelines. Test-retest reliability was determined in 99 students with a time interval of 2.5 weeks. To determine discriminative valid-ity of the Dutch VISA-P, 18 healthy students, 15 competitive volleyball play-ers (at-risk population), 14 patients with patellar tendinopathy, 6 patients who had surgery for patellar tendinopathy, 17 patients with knee injuries other than patellar tendinopathy, and 9 patients with symptoms unrelated to their knees completed the Dutch VISA-P.

Results: The Dutch VISA-P questionnaire showed satisfactory test-retest reliability (ICC = 0.74). The mean (± SD) VISA-P scores were 95 (± 9) for the healthy students, 89 (± 11) for the volleyball players, 58 (± 19) for patients with patellar tendinopathy, and 56 (± 21) for athletes who had surgery for patellar tendinopathy. Patients with other knee injuries or symptoms unrelated to the knee scored 62 (± 24) and 77 (± 24).

Conclusion: The translated Dutch version of the VISA-P questionnaire is equivalent to its original version, has satisfactory test-retest reliability and is a valid score to evaluate symptoms, knee function and ability to play sports of Dutch athletes with patellar tendinopathy.

Dutch translation of the VISA-P questionnaire 43

4

Background

Jumper’s knee (patellar tendinopathy) is an insertional tendinopathy most commonly af-fecting the patellar tendon’s origin on the inferior pole of the patella.1 Prolonged repeti-tive stress of the knee extensor apparatus can lead to this overuse tendinopathy of the patellar tendon inathletes from different sports.2 Prevalence of patellar tendinopathy is especially high in jumping sports.3

There is no consensus on what is the most appropriate treatment for patellar tendinopa-thy.4-6 Exercise-based conservative treatment, including specific eccentric strengthening exercises, is considered to be useful in a rehabilitation program for patients with patel-lar tendinopathy.7 However, further research is necessary to determine the most effective treatment strategies.The VISA-P questionnaire has been introduced to quantify athletes’ disability due to pa-tellar tendinopathy, thereby facilitating research into this condition.8 This self-adminis-tered brief questionnaire assesses symptoms, simple functional tests and ability to play sports. It has been proven to be a valid and reliable instrument for documentation of recovery from patellar tendinopathy.9,10 It is claimed to determine clinical severity but is not a diagnostic tool.The VISA-P questionnaire is an English-language questionnaire developed in Australia. It has already been translated into and adapted for a Swedish and an Italian version.11,12 Aim of this study was to translate the questionnaire into Dutch and to study the reliabil-ity and validity of the Dutch version of the VISA-P.

Methods

The VISA-P questionnaireThe VISA-P questionnaire consists of eight questions (see Appendix B). Six out of eight questions rate pain during activities of daily living and simple functional tests on an inversed visual analogue scale from 0 to 10 points, with 10 representing optimal health. Two questions concern the ability to participate in sporting activities. The maximum VISA score for an asymptomatic athlete is 100 points.

Translation procedureThe VISA Tendon Study Group in Australia was informed and gave their consent to a Dutch translation of the VISAP questionnaire (Jill Cook, personal communication, 2008). The VISA group slightly modified the original version by changing the time periods in question 8 (Jill Cook, personal communication, 2008). It was therefore decided to translate the modified version.The English VISA-P was translated according to the method described by Beaton et al.13 This method recognises 5 stages: (1) translation, (2) synthesis, (3) back translation, (4) ex-pert committee review and (5) pre-testing. Two students (one informed, one uninformed) independently translated the questionnaire into Dutch (stage 1). At stage 2, a synthesis

44 Chapter 4

was made of these two translations. Back translation (stage 3) was done independently by two native English speakers fluent in Dutch, one with a medical background and one without. The expert committee consisting of two translators from stages 1 and 3, a sports medicine physician and a human movement scientist/epidemiologist drafted the final ver-sion (stage 4), which was pre-tested on eight persons.

SubjectsAll subjects were asked for demographic characteristics (gender, age, height, weight and sport hours per week).

ReliabilityTo assess test-retest reliability, 99 students filled out the Dutch VISA-P twice, at an inter-val of 2.5 weeks.

ValidityTo determine discriminative validity of the Dutch VISA-P, 89 persons completed it. They were divided into six groups: (1) 18 healthy students, (2) 15 competitive volleyball play-ers (at-risk population), (3) 14 patients with the of diagnosis patellar tendinopathy, (4) 6 patients who had surgery for patellar tendinopathy 6 months before, (5) 17 patients who had knee injuries other than patellar tendinopathy, and (6) 19 patients with symptoms unrelated to their knees. All patients were treated at the Center for Sports Medicine, Uni-versity Medical Center Groningen, The Netherlands. The study was conducted according to the regulations of the Medical Ethical Committee at University Medical Center Gron-ingen.

StatisticsDescriptive statistics (mean, SD) were used to describe the subject characteristics.

ReliabilityInternal consistency was determined with Cronbach’s alpha. A principal component anal-ysis with varimax rotation was carried out to analyse the factor structure (eigen value above 1). Intraclass correlation coefficients (ICCs) were calculated to analyse test-retest reliability, and Bland and Altman plots were constructed.

ValidityDifferences between the six groups were analysed with an ANOVA. The Bonferroni meth-od was applied to correct for multiple testing in the post-hoc analyses. All statistical anal-yses were carried out using SPSS version 16.0. A significance level of 5% was applied.


4

Results

TranslationThe expert committee agreed with the translation and back-translation. Only the transla-tion of the words in questions 4 and 5 was debated. Dutch athletes often use the English words ‘lunge’ and ‘squatting’ for these specific exercises instead of the Dutch translation (uitvalspas and hurkbeweging). Therefore it was decided to include both the English word and the Dutch translation. Pre-testing did not reveal any difficulties. For the Dutch VISA-P see Appendix C.

Subjects ReliabilityOf the 99 students who completed the VISA-P the First time, 71 filled it in the second time. The mean VISA-P score of the 28 drop-outs did not differ significantly from that of the first assessment of the 71 students. Of these 71 students, 53 (75%) were female. Mean age was 19.2 (± 0.9) years, mean height 1.75 (± 0.07) m, mean weight 67.4 (± 10.0) kg, and mean hours of sports activities per week 5.36 (± 4.1). The mean VISA-P score (± SD) was 89.5 (± 14.3) and 90.3 (± 14.2) at the first and second assessments, respectively. The ICC between the first and second assessments was 0.74 (P < 0.001). When looking at the individual questions, five out of eight questions had an ICC > 0.60 (range 0.45–0.82). Bland and Altman plot (Figure 4.1) shows that zero lies within the 95% CI of the mean difference, indicating that no bias had occurred.

Mean first and second assessment

Mea

n di

ffer

ence

( se

cond

- fi

rst a

sses

smen

t)

95% CI of difference

100,00

80,00

60,00

40,00

20,00

0,00

-20,00

-40,00

-60,00

-80,00

-100,00

40,00 50,00 60,00 70,00 80,00 90,00 100,00

Figure 4.1. Bland & Altman plot.

46 Chapter 4

Table 4.1. Principal component analysis with varimax rotation, forced three-factor structure.

Component

1 2 3

Q1 0.21 0.05 0.94

Q2 0.89 0.11 0.15

Q3 0.80 -0.24 0.10

Q4 0.75 0.42 0.14

Q5 0.69 0.48 0.17

Q6 0.71 0.37 0.33

Q7 0.01 0.78 -0.09

Q8 0.24 0.68 0.35

Table 4.2. VISA-P scores and demographic characteristics (means (SD)) of the participants of the validity study.

Healthy students

At-risk population

Injury other than

knee

Knee injury Patellar tendino-

pathy

Surgery forpatellar tendino-

pathy

Total

N 18 15 19 17 14 6 89

VISA-P 95.3 (8.8) 88.6 (11.1) 76.6 (24.3) 61.9 (24.1) 58.2 (18.9) 56.0 (20.9) 75.3 (23.6)

Male (%) 7 (38.9) 8 (53.3) 4 (21.1) 11 (64.7) 11 (78.6) 5 (83.3) 46 (51.7)

Age (yrs) 20.0 (1.5) 25.2 (4.7) 19.2 (1.2) 24.7 (4.5) 25.1 (3.7) 32.5 (2.9) 23.0 (4.7)

Height (m) 1.76 (0.08) 1.87 (0.08) 1.77 (0.07) 1.84 (0.09) 1.85 (0.09) 1.81 (0.08) 1.81 (0.09)

Weight (kg) 69.9 (9.5) 82.0 (12.6) 69.2 (12.3) 82.1 (12.1) 80.5 (12.4) 93.3 (1.5) 77.0 (13.1)

Sport (hours/week)

5.1 (3.3) 8.0 (2.9) 5.6 (4.4) 3.8 (3.1) 4.5 (3.1) 1.0 (1.7) 5.2 (3.7)


4

The Cronbach’s alpha was 0.73 for the first and 0.71 for the second assessment. The principal component factor analysis yielded a two-factor structure, explaining 64.5% of the total variance. The question about sitting pain-free had the lowest factor score (0.53). Forcing a three-factor structure, explaining 74.6% of total variance, resulted in one com-ponent with five questions (pain during activities), a second component with two ques-tions (physical activity participation), and a third component with only one question (pain during sitting). The lowest factor score was 0.68 (see Table 4.1).

ValidityMean VISA-P scores (± SD) and characteristics of the participants in the six different groups are displayed in Table 4.2. ANOVA revealed a significant difference between the six groups (F = 10.7, p < 0.001). When looking at the eight questions separately, on ques-tions 1 and 3 no significant difference was seen (p = 0.20 and 0.16, respectively). Posthoc analyses (Bonferroni correction) revealed that the mean VISA-P score of the group with patellar tendinopathy differed significantly from that of the healthy students group and the elite volleyball players (at-risk group), but not from the other three groups

Discussion

TranslationWe feel confident that the translated Dutch VISA-P questionnaire is linguistically equiva-lent to the original version, since our study shows that the VISA-scores of both healthy subjects (95) and athletes with patellar tendinopathy visiting a sports medicine clinic (58) are comparable with the results of Visentini (95 and 55 respectively).8 Also, the expert translation committee judged the original and translated versions to be congruent.

ReliabilityOver a time interval of 2.5 weeks, the Dutch version of the VISA-P score showed satisfac-tory test-retest reliability (ICC = 0.74). This is slightly lower than in previous studies,8,11,12 which had much shorter test-retest intervals, ranging from 1 hour to 1 week. We decided to take a longer time interval in order to prevent participants from copying the VISA-P from memory. A time interval of two weeks or more is commonly used in reliability studies. We are aware that a limitation of this study is that the test-retest reliability was investigated in asymptomatic students. One could argue that testing reliability in athletes with patellar tendinopathy would have been more appropriate. However, in the reliability study of Frohm the majority of participants (66%) who were asked to fill out the VISA-P questionnaire were asymptomatic too.11 No differences with regard to reliability were de-scribed between symptomatic and asymptomatic participants, therefore we believe that the reliability of the Dutch VISA-P questionnaire found in this study also applies to ath-letes with patellar tendinopathy.

48 Chapter 4

ValidityThe mean VISA-P score varied significantly between the groups of healthy and injured subjects. As mentioned before, the VISA-P scores in this study were comparable with those from the original study of Visentini.8 Healthy volunteers had VISA-P scores of 95 in both studies, and athletes with patellar tendinopathy also had comparable scores of 55 and 58. The VISA-P score of volleyball players (population at risk) in this study was within the same range as the score of the basketball players in the original publication, 89 and 92 respectively. Patients with other knee injuries (62) and even subjects with other injuries not related to the knee (77) also had low scores compared to healthy subjects. This indicates that the VISA-P is indeed not suitable for diagnostic use.The VISA-P was developed to monitor – by intra-individual comparisons – the effective-ness of treatment and rehabilitation programmes in athletes with patellar tendinopathy as well as for research purposes to facilitate group comparisons. Although this study was not designed to investigate the sensitivity of the VISA-P score for change, there seems to be sufficient range between healthy subjects and athletes with patellar tendinopathy to detect differences. On a maximum of 100 points, healthy subjects scored 95 points compared to 58 in athletes with patellar tendinopathy.Translation of the VISA-P questionnaire into the Dutch language now makes it possible to compare results from international studies with the Dutch situation. For example, in this study subjects who underwent surgery because of their patellar tendinopathy scored ‘only’ 56 points. In our department athletes only proceed to surgery if conservative treat-ment has failed and they still have pain during daily activities, experience painful func-tional tests and are unable to participate in sports at the desired level (VISA-P score approximately < 40). This is in line with previous findings by Bahr, who found a mean VISA-P score of 58 in patients who had a patellar tenotomy for six months (and a pre-surgical score of 31).14 Our results show that the Dutch version of the VISA-P score conveys the same informa-tion as that gathered by other international versions of this questionnaire. This validated and reliable questionnaire will not only facilitate patellar tendinopathy research in the Netherlands, it also allows international comparison.

Conclusion

The results of the present study indicate that the translated Dutch version of the VISA-P questionnaire is equivalent to its original version, has satisfactory test-retest reliability, and is a valid score to evaluate symptoms, functional tests and ability to play sports of Dutch athletes with patellar tendinopathy.


4

References

1. Blazina ME, Kerlan RK, Jobe FW, Carter VS, Carlson GJ (1973). Jumper’s knee. Orthop Clin North Am; 4:665-78.

2. Kannus P (1997). Etiology and pathophysiology of chronic tendon disorders in sports. Scand J Med Sci Sports; 7:78-85.




6. Zwerver J (2008). [Patellar tendinopathy (‘jumper’s knee’); a common and difficult-to-treat sports injury]. Ned Tijdschr Geneeskd; 152:1831-7.



9. Khan KM, Maffulli N, Coleman BD, Cook JL, Taunton JE (1998). Patellar tendinopathy: some aspects of basic science and clinical management. Br J Sports Med; 32:346-55.


11. Frohm A, Saartok T, Edman G, Renstrom P (2004). Psychometric properties of a Swedish translation of the VISA-P outcome score for patellar tendinopathy. BMC Musculoskelet Disord; 5:49.

12. Maffulli N, Longo UG, Testa V, Oliva F, Capasso G, Denaro V (2008). VISA-P score for patellar tendinopathy in males: adaptation to Italian. Disabil Rehabil; 30:1621-4.

13. Beaton DE, Bombardier C, Guillemin F, Ferraz MB (2000). Guidelines for the process of cross-cultural adaptation of self-report measures. Spine; 25:3186-91.

14. Bahr R, Fossan B, Loken S, Engebretsen L (2006). Surgical treatment compared with eccentric training for patellar tendinopathy (Jumper’s Knee). A randomized, controlled trial. J Bone Joint Surg Am; 88:1689-98

Chapter 5

Biomechanical analysis of the single-leg

decline squat

J. Zwerver S.W. Bredeweg

A.L. Hof

Br J Sports Med. 2007 Apr;41(4):264-8.

52 Chapter 5

Abstract

Background: The single-leg squat on a 25° decline board has been described as a clinical assessment tool and as a rehabilitation exercise for patients with patellar tendinopathy. Several assumptions have been made about its working mechanism on patellar load and patellofemoral forces, but these are not sub-stantiated by biomechanical evaluations.

Aim: To investigate knee moment and patellofemoral contact force as a func-tion of decline angle in the single-leg squat.

Methods: Five subjects performed single-leg eccentric squats at decline angles of 0°, 5°, 10°, 15°, 20°and 25° (with/without a backpack of 10 kg), and 30° on a board that was placed over a forceplate. Kinematic and forceplate data were recorded by the Optotrak system. Joint moments of ankle, knee and hip were calculated by two-dimensional inverse dynamics.

Results: Knee moment increased by 40% at decline angles of 15° and higher, whereas hip and ankle moment decreased. Maximum knee and ankle angles increased with steeper decline. With a 10 kg backpack at 25° decline, the knee moment was 23% higher than unloaded. Both patellar tendon and patellofemo-ral forces increased with higher decline angles, but beyond 60°, the patellofemo-ral force rose steeper than the tendon force.

Conclusions: All single-leg squats at decline angles >15° result in 40% in-crease in maximum patellar tendon force. In knee flexions >60°, patellofemoral forces increase more than patellar tendon forces. Higher tendon load can be achieved by the use of a backpack with extra weight.

Biomechanical analysis of the decline squat 53

5

Introduction

Patellar tendinopathy is a common overuse injury, especially in jumping athletes.1 Man-agement of patellar tendinopathy is hampered by lack of valid and reliable diagnostic and reassessment tools. Exercise-based conservative treatment, including specific eccen-tric-strengthening exercises, is considered to be useful in a rehabilitation programme in patients with patellar tendinopathy.2-4

The single-leg squat performed on a decline board (figure 5.1) has been described as a method to maximally load the knee extensors in an eccentric manner. This functional test is considered as a useful clinical assessment tool for patients with patellar tendinopathy.5,6 Furthermore, it is used as an easy and effective rehabilitation exercise for patients with patellar tendinopathy.7-9 Both Purdam et al8 and Young et al9 hypothesised that the supe-rior effectiveness of the eccentric decline squat, compared to a normal eccentric squat on a flat floor, may be the result of the fact that standing in the decline position reduces the contribution of the calf to the squat. In this way, knee extensors and the patellar tendon are maximally loaded. Indeed, in a recent study, Kongsgaard et al10 demonstrated that the use of a 25°decline board increases the load and the strain of the patellar tendon during a single-leg squat. However, this could not be explained by a decreased calf muscle activity, assessed by surface electromyography (EMG). Joint stop angles of ankle and hip changed significantly. They assumed that the less-flexed ankle and hip joints during the decline squat displaces the body’s centre of mass further behind the knee joint axis, thereby increasing the knee extensor moment and thereby the load on the patellar tendon. More-over, it is also unclear why a decline angle of 25°is considered to be the most effective.

Figure 5.1. Eccentric decline squat (informed consent was obtained for publication of this figure).

54 Chapter 5

Based on the results of previous biomechanical studies,11,12 Purdam et al6 recommended not to flex the knee over 50–60° during the decline squat in order to maximise the patellar tendon force while balancing against excessive patellofemoral compression, which occurs at 70°of knee flexion and beyond.6 To our knowledge, no studies about the decline squat have been published that validate these assumptions and recommendations. Therefore, we conducted a study on the biomechanics of the single-leg decline squat. The objective of this study was to investigate knee moment and patellofemoral contact force as a func-tion of decline angle.

Methods

SubjectsTwo male and three female subjects participated in this study. Their ages were between 19 and 24 years (mean 22), their height ranged from 1.68 to 2 m (mean 1.8), and weight from 58 to 84 kg (mean 72). They were all moderately physically active in sports (2–5 h/week), healthy and had no actual or previous problems with the knee, ankle or hip joint. All subjects gave their informed consent for the procedure of the study. Participation was voluntary and in agreement with the local medical ethics committee guidelines.

ProcedureTwo decline boards with the angle adjustable at 0–40° were constructed. The board for the dominant leg was placed on the force plate (Bertec 4060-08, Columbus, Ohio, USA). Kinematics in sagittal view were recorded by an Optotrak (Northern Digital, Waterloo, Canada) optoelectronic system. Lightemitting diodes were attached at the ankle (lateral malleolus), knee (lateral femoral condyle), hip (trochanter major) and shoulder (acromion). Kinematic and force plate data were recorded at 100 Hz by the Optotrak system. Joint moments of ankle, knee and hip were calculated by two-dimensional inverse dynamics13 in Excel.After a 5 min warm-up on a cycle ergometer (Lode Excalibur, Groningen, The Nether-lands) at 75 W, the subject performed two pretest single-leg squats on the decline board to get used to the procedure and to check whether the force plate and positioning system worked correctly. Each subject performed two single-leg decline squats at 0°, 5°, 10°, 15°, 20°, 25°and 30°. Declines of ≥35°proved impracticable because the subject slid down-wards and could not stand upright. All subjects performed the decline squat standing on their dominant leg and flexing their knee, starting from complete extension to maximal flexion. The contralateral leg was kept forward during the downward movement. Sub-jects came back to starting position by placing the contralateral leg on the second decline board and extending this leg. They were instructed to keep their trunk in an upright posi-tion and to avoid lateral weight shift.With the board at a decline angle of 25°, some additional exercises and measurements were carried out: (a) the subject was loaded with an extra weight of 10 kg in a backpack, (b) raising up to starting position with the dominant leg, and (c) keeping the contralateral leg backward instead of forward.


5

Data handlingTo account for differences in weight and stature of the subjects, biomechanical variables were normalised as:normalised force (1)

and normalised moment

(2)

where m is body mass, g is the acceleration of gravity, and h is leg length from trochanter to floor. All moments are presented with extension positive.Knee flexion angle φ is defined as 0 degrees at straight knee, ankle plantarflexion angle ψ as 90 degrees in upright standing. When the subject stands with the hip vertically above the ankle and when upper and lower parts of the leg are about equally long, it holds for the ankle (figure 5.2A):

(3)

where α is the decline angle. (If the hip is not above the ankle—that is, when normalised hip and ankle moments are different—this relation is approximate.)As all knee extensors act by way of the patellar tendon, (normalised) patellar tendon force equals:

(4)

where =d/h is the normalised moment arm of the patellar tendon. For , experimental data of Krevolin et al15 were used, which could be fitted by:

(5)

Assuming that there is no cocontraction by the knee flexor muscles, the patellofemoral contact force Fp-f can be estimated by means of the model of Buff et al,11 which gives the ratio between the quadriceps force Fq and the patellar tendon force Fp, and the angle be-tween them. The patellofemoral force can then be found from the vector diagram (figure 5.2B).

Statistical analysisAll data were analysed using Excel 2003 (Microsoft, USA). Comparisons were performed with use of the unpaired t test. The level of significance was set at 5%.

F = Fm g

M = Mm hg

ψ =90˚_ 2 +α

F = Md

tendon

d 0.022 + 0.03sin(2 )~~

d 0.022 + 0.03sin(2 )~~ d 0.022 + 0.03sin(2 )~~

56 Chapter 5

Figure 5.2. (A) Diagram to show the relationship between decline α, knee joint angle ϕ and ankle angle ψ. Note that ψ - α = 90°- ϕ / 2 (the angle with the dot). (B) Vector diagram to show the relationship between patellar tendon force Fp, quadriceps force Fq and patellofemoral contact force Fp-f. The ratio between Fp and Fq, and the angle between them, were obtained from the model of Buff et al.11 (C) In a static approximation, the moments of hip (H), knee (K) and ankle (A) equal the ground reaction force (GRF) multiplied by the perpendicular distance from the joint to the GRF (dashed lines).

αψ

φφ /2

>

>

>

A

F tendon

Ftendon

F p-f

B

αψ

φφ /2

>

>

>

A

F tendon

Ftendon

F p-f

B

H

GRF

K

A

C

A B C

Figure 5.3. Sample recording of knee, hip and ankle moment (M) as a function of time in two squats.

Time (s)

M(N

m)


5

Results

Figure 5.3 shows a recording of knee, hip and ankle moment. Hip and ankle moment were low during the movement, whereas the knee moment increased strongly with knee flexion during the squats. It was verified that the squatting movement was performed so slowly that contributions to the moments due to accelerations of the limb were always negligible (<4 Nm for the knee, and <8 Nm for the hip). In addition, the ground reaction force (GRF) vector ran perfectly vertical. Figure 5.4 shows the average of the maximum normalised moments, at maximal knee flexion. Knee moment increases, and hip and ankle moments decrease by up to about 15° of the decline board. The differences in knee moment at 0°and 15–30°were statistically significant (p=0.035). Maximum knee angle (figure 5.5) increased from 67° without decline, up to about 83° at declines of ≥15°. Maximum ankle angle increased from 56° (= 34° dorsiflexion) to 81° at the steepest decline.

-0.1

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

-5 0 5 10 15 20 25 30 35

decline (deg.)

norm

aliz

ed m

omen

t

Knee Ankle Hip

Figure 5.4. Normalised moments at maximum knee flexion as a function of decline (bars indicate the range of themeasured values).

Figure 5.5. Maximum knee flexion angle and minimum ankle plantar flexion angle versus decline (bars indicate the range of the measured values).

0

20

40

60

80

100

120

-5 0 5 10 15 20 25 30 35

decline (deg.)

joi

nt a

ngle

(deg

.)

Knee Ankle

58 Chapter 5

The additional exercises did not give significant differences, except for the situation in which the subject was loaded with a 10 kg backpack. In that case, the mean knee moment was 23% (SD 10%, p=0.02) higher than unloaded, and the maximum knee angle was 5°smaller (p=0.04).

Discussion

Knee moment/patellar tendon forceThis study clearly demonstrates that performing a single-leg decline squat on a decline board of ≥15°results in a 40% higher knee moment, and thus patel-lar tendon force, compared to the same exercise on a flat floor. The hip moment is low at all decline angles and the ankle moment decreases with decline (figure 5.4). From the mechanical viewpoint, these findings can be interpreted as follows. As the GRF vector ran vertical, and inertial components to the moments were negligible, joint mo-ments are closely equal to the magnitude of the GRF multiplied by the horizontal distance from the joint to the GRF vector (figure 5.2C). With greater decline angles, the GRF is moved further from the knee joint, thus increasing the knee extensor moment. In addition, the knee can be flexed more in a decline position (figure 5.5).In our opinion, the higher knee moment and better knee flexion on a steeper decline can be explained by properties of the ankle. At 0° or 5° decline, the ankle is in extreme dor-siflexion, around 56°. In this position, the passive ankle moment is considerable, in fact of the order of the measured values.16 This high ankle moment implies a more anterior position of the GRF, and therefore the knee moment will be lower as a consequence of the extreme dorsiflexion. In addition, this is uncomfortable to the subject, who can experience a tight feeling in the calf. The second reason is that the ankle, knee and decline angles are related according to equation 3. When, therefore, ankle dorsiflexion is restricted, the knee cannot be flexed maximally without a decline. Although Kongsgaard et al10 also found that patellar load increased during a decline squat, they discussed that this could not be explained by a decrease in the ankle moment, as they had found equal EMG values for gastrocnemius and soleus with and without a decline. In our opinion, this argument is not convincing because research shows that a passive ankle moment exists at relevant dorsiflexion angles.16 In addition, the active force–length relation of the muscle changes with ankle angle, and hence also the ratio between EMG and ankle moment.16-18

The additional exercises with different postures of the contralateral leg showed no ad-vantages. Only the addition of a 10 kg backpack showed a 23% increase in knee moment. This is in fact more than expected: 10 kg is 14% of the average body weight of 72 kg. This is because the load is located posterior to the unloaded body centre of mass, and thus has a larger moment arm relative to the knee.

Patellofemoral contact forceThe aim of the single-leg decline squat is to achieve a maximal patellar tendon force. A point of concern is that the patellofemoral contact force should not become excessive,


5

as this may lead to the patellofemoral pain syndrome.19 When ankle and hip moment are assumed to be zero, it holds for the normalised knee moment.

(6)

The theoretical tendon and patellofemoral forces can be calculated with the estimated mo-ment arm (equation 5) and the model of Buff et al11 (figure 5.6). Both increase with higher decline angles, but beyond 60°, the patellofemoral force rises steeper than the tendon force. At 60°, the patellofemoral contact force is already nine-times the body weight, a fur-ther increase seems undesirable. Knee flexion >60° should thus better be avoided. When a higher tendon force is required, it may be better to give an additional backpack load. Practical consequencesOur experiments demonstrate that performing single-leg squats at decline angles >15° all result in a significant increase in the maximum patellar tendon force. Any decline board between 15° and 30° can thus be used, whichever feels most comfortable to the patient. To prevent patellofemoral pain syndrome, we recommend avoiding knee flexions >60°. In case a higher tendon load is required, we recommend the use of a backpack with extra weight.

Abbreviations: EMG: electromyography; GRF: ground reaction force

AcknowledgementsWe thank A Kingma, M Slotman and M Uitman for executing the experiments.

M 0.5sin (2 )~~

Figure 5.6. Calculated force (F) in the tendon (Fp; solid line) and patellofemoral contact force (Fp-f; dashed line) as a function of knee angle.

0

2

4

6

8

10

12

14

16

18

0 20 40 60 80 100 120

knee angle (deg.)

F/bo

dy w

t.Ftendon Fp-f 80 deg. 60 deg

60 Chapter 5

References 1. Lian OB, Engebretsen L, Bahr R (2005). Prevalence of jumper’s knee among elite athletes

from different sports: a cross-sectional study. Am J Sports Med; 33:561-7.

2. Cannell LJ, Taunton JE, Clement DB, Smith C, Khan KM (2001). A randomised clinical trial of the efficacy of drop squats or leg extension/leg curl exercises to treat clinically diagnosed jumper’s knee in athletes: pilot study. Br J Sports Med; 35:60-4.

3. Jensen K, Di Fabio RP (1989). Evaluation of eccentric exercise in treatment of patellar tendinitis. Phys Ther; 69:211-6.

4. Stanish WD, Rubinovich RM, Curwin S (1986). Eccentric exercise in chronic tendinitis. Clin Orthop Relat Res;65-8.

5. Cook JL, Khan KM, Maffulli N, Purdam C (2000). Overuse tendinosis, not tendinitis part 2. Applying the new approach to patellar tendinopathy. Physician and Sportsmedicine; 28:31-+.

6. Purdam CR, Cook JL, Hopper DM, Khan KM, VIS tendon study group (2003). Discriminative ability of functional loading tests for adolescent jumper’s knee. Physical Therapy in Sport; 4:3-9.

7. Jonsson P, Alfredson H (2005). Superior results with eccentric compared to concentric quadriceps training in patients with jumper’s knee: a prospective randomised study. Br J Sports Med; 39:847-50.

8. Purdam CR, Jonsson P, Alfredson H, Lorentzon R, Cook JL, Khan KM (2004). A pilot study of the eccentric decline squat in the management of painful chronic patellar tendinopathy. Br J Sports Med; 38:395-7.

9. Young MA, Cook JL, Purdam CR, Kiss ZS, Alfredson H (2005). Eccentric decline squat protocol offers superior results at 12 months compared with traditional eccentric protocol for patellar tendinopathy in volleyball players. Br J Sports Med; 39:102-5.

10. Kongsgaard M, Aagaard P, Roikjaer S, Olsen D, Jensen M, Langberg H, Magnusson SP (2006). Decline eccentric squats increases patellar tendon loading compared to standard eccentric squats. Clin Biomech (Bristol , Avon ); 21:748-54.

11. Buff HU, Jones LC, Hungerford DS (1988). Experimental determination of forces transmitted through the patello-femoral joint. J Biomech; 21:17-23.

12. Huberti HH, Hayes WC, Stone JL, Shybut GT (1984). Force ratios in the quadriceps tendon and ligamentum patellae. J Orthop Res; 2:49-54.

13. Hof AL (1992). An explicit expression for the moment in multi-body systems. J Biomechan-ics; 25:1209-11.

14. Hof AL (1996). Scaling gait data to body size. Gait and Posture; 4:222-3.

15. Krevolin J, Pandy M, Pearce J (2004). Moment arm of the patellar tendon in the human knee 107. Journal of Biomechanics; 37:785-8.


5

16. Hof AL, Berg Jwvd (1981). EMG to force processing II: Estimation of parameters of the Hill muscle model for the human triceps surae by means of a calf ergometer. J Biomechanics; 14:759-70.

17. Nourbakhsh MR, Kukulka CG (2004). Relationship between muscle length and moment arm on EMG activity of human triceps surae muscle. J Electromyogr Kinesiol; 14:263-73.

18. Sanderson DJ, Martin PE, Honeyman G, Keefer J (2006). Gastrocnemius and soleus muscle length, velocity, and EMG responses to changes in pedalling cadence. J Electromyogr Kinesiol; 16:642-9.

19. Macdonald DA, Hutton JF, Kelly IG (1989). Maximal isometric patellofemoral contact force in patients with anterior knee pain. J Bone Joint Surg Br; 71:296-9.

Chapter 6

Extracorporeal shockwave therapy for patellar

tendinopathy: a review of the literature

M.T. van Leeuwen J. Zwerver


Br J Sports Med. 2009 Mar;43(3):163-8.

64 Chapter 6

Abstract

Background: Extracorporeal shockwave therapy (EWST) has become a pop-ular treatment for patellar tendinopathy.

Aim: The aim of this review was to study the effectiveness of ESWT treat-ment for patellar tendinopathy; to draft guidelines for an effective treatment protocol of ESWT treatment; and to identify topics for further research.

Methods: A computerised search of the Medline and Embase databases was conducted on 1 August 2007, to identify studies dealing with the effectiveness of ESWT for patellar tendinopathy.

Results: Seven articles describing the effectiveness of ESWT on patellar ten-dinopathy, all published after 2000, were included. These studies included a total of 283 patients (298 tendons), 204 of whom (215 tendons) were assigned to ESWT treatment. The treatment results were positive but most studies had methodological deficiencies, small numbers and/or short follow-up periods. Method of application and shockwave generation, energy level, number and frequency of treatments, use of (local) anaesthesia and method of localisation were variable.

Conclusion: ESWT seems to be a safe and promising treatment for patel-lar tendinopathy with a positive effect on pain and function. Based on current knowledge it is impossible to recommend a specific treatment protocol. Further basic and clinical research into the working mechanism and effectiveness of ESWT for patellar tendinopathy are necessary.

ESWT for patellar tendinopathy 65

6

Introduction

Patellar tendinopathy, also called jumper’s knee, is a chronic overuse injury of the patel-lar tendon causing pain at the inferior pole of the patella.1 The prevalence is particularly high in athletes.2,3 Among elite volleyball and basketball players a prevalence over 40% has been described.4 Because of its chronicity and a lack of consensus about which treat-ment is the most adequate,4,5 patellar tendinopathy has a major impact on the career of many athletes and for some it is the reason to end their career prematurely.2,6,7

The aetiology of patellar tendinopathy is not completely understood, but repetitive over-load is thought to be an important factor.8,9 Histopathological examinations of affected patellar tendons revealed the absence of inflammatory cells and no increased levels of prostaglandin.8 Consequently, the former term tendinitis should be replaced by tendino-sis, which reflects the underlying process of tendon degeneration and the failed healing response.10 The term tendinopathy is now often used clinically.10

Based on the present literature it is not possible to decide what is the most appropriate and effective treatment for patellar tendinopathy.11,12 The results of the many conserva-tive treatments are not always consistent or evidence-based.7,8,13-15 Eccentric training has been proposed as the best conservative treatment, but results are not convincing.7 When conservative treatment fails, most patients proceed to surgical treatment,11,12 which ac-cording to Bahr et al produces excellent or good results in at most 45% of patients.4

Since the early 1990s, extracorporeal shockwave therapy (ESWT) has been used for the treatment of several chronic tendinopathies.16 This non-invasive and safe thera-py originates from urology, where it is used to pulverise kidney stones (lithotripsy).17 In some studies, ESWT has shown promising results in the treatment of rotator cuff tendinopathy, extensor tendinopathy of the elbow and chronic plantar fasciitis.16-20 ESWT is nowadays used as a treatment for patellar tendinopathy as well. The under-lying working mechanism of ESWT on tendinopathies is not completely understood, though. Both an analgesic effect and a stimulating effect on tissue regeneration have been suggested as possible working mechanisms.19,21,22 There is no consensus about ESWT treatment protocols.16 Controversy exists about method of application and shock-wave generation (focused or radial), energy level to be used, number and frequency of treatments, use of (local) anaesthesia and method of localisation (see table 6.1).16,19 The main purpose of this review was to study the effectiveness of ESWT treatment for patellar tendinopathy. The ultimate goal is to draft guidelines for an effective treatment protocol and to identify topics for further research.

66 Chapter 6

Materials and methods

Literature searchA computerised search of the Medline and Embase databases was conducted on 1 Au-gust 2007 (for search terms see figure 6.1). The search was limited to literature published in English or German. There was no limitation for publication year. Animal studies were excluded. Articles were defined to be relevant for this review if their subject was ESWT for patellar tendinopathy. Further, all reference lists were hand-searched for other rel-evant articles. The selected articles were reviewed by the authors and judged on their relevance and contribution to the subject of this study. All seven studies published about ESWT for patellar tendinopathy were included. All authors independently assessed the methodological quality of these seven studies using the Delphi criteria.24 Keywords were: patellar tendinopathy, jumper’s knee, shockwave therapy, treatment, review

Table 6.1. Variables of influence on the effectiveness of ESWT

Variables Details

Shockwave generation:16-19,23

Focussed shockwaveRadial pressure wave

Site of most effects:DepthSuperficial

Energy level (mJ/mm2):16,23

Low (< 0.08)Medium (0.08 – 0.28)High (> 0.6)

With an energy level of >0.6 mJ/mm2 therapy will be painful and macroscopic lesions will appear. 16

Number of treatments, time interval between treatments and shockwave frequency

If there is more than 1 treatment, effects will be cumulative.15

Whether or not anaesthetics are used. When using anaesthetics, a larger energy level can be

used.16

Method of localisation:19

Anatomical

Image-guided focusing

Clinical

Can be difficult with obese patients or when the anatomy is disrupted as a result of surgery.19

Very specific method, however the site of the lesion is not always consistent with the site where the most pain is experienced.19

Shockwaves are applied directly to the site where the most pain is experienced. This method of localisation is not possible when using a local anesthetic.19


6

Results

We found seven articles in which the effectiveness of ESWT on patellar tendinopathy was described, all published after 2000. These studies included a total of 283 patients (298 tendons), 204 of whom (215 tendons) were assigned to ESWT treatment. The main study characteristics are presented in table 6.2.

Description of the studiesIn 2000 Vara et al studied the effectiveness of different ESWT energy levels for patel-lar tendinopathy in 27 patients. In this prospective, randomised, single-blind trial, one group received from one to five treatments with an energy level of 0.105–0.437 mJ/mm2. Another group (placebo) received one treatment with an energy level of 0.04 mJ/mm2. Evaluation 2 years after the last treatment showed an improvement of 61% in the study

Results of search strategy in Medline: (shock[TI] AND wave[TI]) OR shockwave[TI] OR eswt[TI]) AND treatment AND "review"[Filter] and Results of search strategy in Medline: (jumper's knee OR patellar tendinopathy OR (patella* AND tendinopath*) OR (jumper* knee)) AND (extracorporeal shockwave OR eswt OR rswt OR shockwave OR shock wave) :

↓ n = 207

Results of search strategy in Embase: ('patella tendinopathy' OR 'jumpers knee' OR 'patellar tendinopathy' OR (patella* AND tendinopath*) OR (jumper* AND 'knee'/syn)) AND ('extracorporeal shockwave' OR eswt OR shock wave OR 'shock wave'/syn OR 'extracorporeal lithotripsy'/syn) :

Results of search strategy in Embase: ('patella tendinopathy' OR 'j umpers knee' OR 'patellar tendinopathy' OR (patella* AND tendinopath*) OR (jumper* AND 'knee'/syn)) AND ('extracorporeal shockwave' OR eswt OR shockwave OR 'shock wave') :

↓ n = 23

Total studies found after literature search

↓ n = 230 _____________________________________________________________________ Studies included after reading the title and abstract

↓ n = 20 ( of which 5 with the subject ESWT in pat. tendinopathy) _____________________________________________________________________ Results after hand-search in reference lists for relevant articles

↓ n = 13( of which 2 with subject ESWT in pat. tendinopathy) _____________________________________________________________________ Total studies included

n = 33( of which 7 with the subject ESWT in pat. tendinopathy

Figure 6.1. Literature search

68 Chapter 6

group for VAS score, pressure pain and functional improvement. In the placebo group there was 7.5% improvement, and 74% and 15% of the patients in the study group and placebo group, respectively, thought the results were good or satisfactory. A limitation of this study was that it was not a double-blind trial, so patients knew whether they received placebo treatment or real treatment. This study showed good results in favour of the group that received ESWT treatment with an energy level of 0.105–0.437 mJ/mm2, but the results could be biased, as a single-blind protocol was used.25

In a non-randomised, prospective pilot study in 2002 by Lohrer et al the effectiveness of radial shockwave therapy (RSWT) on patellar tendinopathy was evaluated in 45 patients who had not responded successfully to previous conservative treatments. Treatment con-sisted of from three to five RSWT sessions with an energy level from 0.06 to 0.18 mJ/mm2. Pain at rest, pain during exercise, pressure pain (all VAS score) and pain-free run-ning time (min) were evaluated after 1, 4, 12, 26 and 52 weeks. During 1 year all scores improved significantly. One year after the last treatment 40% of the patients with patellar tendinopathy were pain-free, 24.4% had improved, and 36.5% of the patients showed no improvement. Although Lohrer et al did not include a control group for comparison purposes, they concluded that ESWT does have a therapeutic effect on patellar tendi-nopathy.26 In 2003 Peers et al retrospectively compared results of surgical treatment with ESWT for patellar tendinopathy in 27 patients (28 tendons). None of the patients had shown improvement after previous conservative treatment. After three ESWT sessions of 0.08 mJ/mm2 in 14 patients (15 knees) and after tenotomy of the patellar tendon with resection of degenerative tissue in 13 patients, VAS and VISA scores, Roles & Maudsley (R&M) classification, length of the rehabilitation period and absence from work were evaluated. Two years after treatment no significant difference in VAS and VISA scores or R&M classification was found, but the surgical treatment group did have a longer absence from work period postsurgically. A limitation of this study was lack of randomisation, so a se-lection bias may have possibly influenced the results. For patients it is difficult to choose between surgery and undergoing ESWT. The risk of complications, intensive postopera-tive rehabilitation and a considerable period of sick leave has to be considered. These factors may have influenced results in favour of the ESWT group. After this study, Peers et al concluded that ESWT is a good alternative to surgical treatment when conservative treatment fails in chronic patellar tendinopathy.6

In 2003 Peers wrote a thesis about the effectiveness of ESWT in Achilles and patellar tendinopathy. In a randomised clinical trial he compared focused ESWT treatment, con-sisting of three sessions with an energy level of 0.2 mJ/mm2, with a placebo treatment (three sessions with an energy level of 0.03 mJ/mm2). The study group consisted of 21 patients; the control


6

Table 6.2. Summary of studies on ESWT and patellar tendinopathy

Author Publication year

Vara F et al25

2000 AbstractLohrer H et al26

2002Peers KHE et al6

2003

Study design Randomised clinical trial, single-blind

Non-randomised, prospective pilot study

Retrospective cross-sectional analysis

Outcome measures VAS score, pressure pain, functional improvement

Pain at rest, pain during exercise and pressure pain (all VAS scores), and pain-free running time (min).

VISA score, VAS score and R&M classification.

Follow-up period in months

24 12 24

Number of patients (total/study group)

27/14 45/45, all athletes 27/14 (28/15 tendons), all athletes

Duration of symptoms in months

≥ 6 13.9

Severity before ESWT VAS 1.6VAS 5.5 (pressure pain) VAS 5.5 (during exercise) pain-free running time 10.4 min

Previous treatment before ESWT

Two of the following treatments: NSAIDs, physical therapy, steroid injections, patellar bracing, acupuncture or immobilisation

Two of the following treatments: NSAIDs, physical therapy or steroid injections

ESWT type DolorclastRadial

Siemens Sonocur Focussed

Energy level (mJ/mm2) 0.105-0.437 (medium) 0.06-0.18 (low-medium) 0.08 (medium)

Number of treatments 1-5 3-5 (2000 imp) 3 (1000imp)

Local anaesthetic none none

Method of localisation patient-guided feedback image guiding

Additional treatment after ESWT

none none

Mean VAS and VISA after ESWT (improvement)

VAS 0.3* (1.3) VAS 1,7* pressure pain (31.8)VAS 1,9* during exercise (3.6) painfree running time 70.3 min (59.9)

VAS 1VISA 83.9

Improved patients (%) 74% (11/14) improved good and satisfactory

64.4% (29/45) improved,pain-free of less pain

66% (10/15) improved,excellent and good

Significant differences in advantage of ESWT treatment

Yes Yes No significant difference between ESWT treatment and surgical treatment

Delphi Score 3 2 3

Conclusion Good results in favour of the group that received ESWT treatment with an energy level of 0.105–0.437 mJ/mm2

ESWT does have a therapeutic effect on patellar tendinopathy

ESWT treatment is a good alternative for surgical treatment when conservative treatment fails for chronic patellar tendinopathy

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Table 6.2. Continued

Author Publication year

Peers KHE27

2003Taunton KM et al28

2003Wang CJ et al15

2007 Vulpiani MC et al142007

Study design Randomised clinical trial Randomised clinical trial

Randomised clinical trial

Non-randomised, prospective cohort study

Outcome measures VISA score, VAS score, R&M classification and functional improvement

VISA score and vertical jump test.

VISA score, VAS score, R&M classification, functional improvement and echo image of patellar tendon.

VAS score, subjective clinical evaluation range

Follow-up period in months

3 3 36 > 24

Number of patients (total/study group)

41/21, all athletes 20/10, all athletes 50/27 (54/30 tendons), all athletes

73/73 (83/83 tendons),15 athletes

Duration of symptoms in months

23 ≥ 3 16.2 ≥ 3

Severity before ESWT VAS 5VISA 46.5

VISA 54.4 VAS 6.0VISA 42.57

VAS 7.1

Previous treatment before ESWT

NSAIDs, physical therapy, steroid injections or patellar taping

NSAIDs Steroid injections. NSAIDs or physiotherapy

ESWT type Sonocur Plus SiemensFocussed

Siemens Sonocur Focussed

OssaTronFocussed

STORZ Medica Focussed

Energy level (mJ/mm2)

0.2 (medium) 0.17 (medium) 0.18 (medium) 0.08- 0.44 (low-high)

Number of treatments

3 (1000 imp) 3-5 (2000 imp) 1 (1500 imp) 3-5 (1500-2500 imp)

Local anaesthetic none none none none

Method of localisation

image guiding palpation palpation, control by imaging

Additional treatment after ESWT

Eccentric training, single leg decline squat

none none none

Mean VAS and VISA after ESWT (improvement)

VAS 3 (2.0)VISA 74.74* (28.24)

VISA 61.4*(7.0) VAS 0.59* (5.41)VISA 92.0* (44.43)

VAS 1.35* (5.75)

Improved patients (%)

61.9% (13 / 21) improved,excellent and good

70% (7/10) improved,less pain, function improved

90.1% (27/30) improved, excellent and good

79.9% (66/83) improved and satisfied

Significant differences in advantage of ESWT treatment

Yes, except for VAS score and R&M classification

Yes Yes, except for diameter and appearance of patellar tendon

Yes

Delphi Score 7 4 6 2

Conclusion ESWT positively contributed to the improvement of pain and function in the short-term treatment of patellar tendinopathy

ESWT treatment could be of value as an additional treatment to other conservative treatments, like eccentric training

ESWT was more effective and safer than conservative treatment in patients with chronic patellar tendinopathy

ESWT seems to be encouraging in light of the long-lasting improvement of the pain symptomatology


6group included 20 patients. Evaluation after 12 weeks was performed using VISA score, R&M classification and degree of functional impairment. There was a significant im-provement in pain and function after ESWT treatment of 0.2 mJ/mm2. Another evalua-tion variable was the VAS score, but for this variable no significant difference was found. In this study the follow-up lasted only 3 months, so no conclusion could be drawn for the long-term benefit. Another limitation of this study was that no limits were set on the severity of patellar tendinopathy at inclusion, so patients with mild or severe complaints were both included in this study. One might argue that patients with only mild complaints had a better prognosis and consequently influenced the results positively, but, because a strict randomisation was applied, patients with only mild complaints were found in both groups. Peers concluded that ESWT positively contributed to improvement of pain and function in the short-term treatment of patellar tendinopathy.27

In 2003 Taunton et al evaluated the effects of ESWT for patellar tendinopathy. In a ran-domised clinical trial, 10 patients in the study group received from three to five focused ESWT treatments with an energy level of 0.17 mJ/mm2. In the control group, 10 patients underwent the same treatment procedure but with an absorbing pad between skin and probe, so only a placebo treatment was given. Evaluation up to 12 weeks after the last treatment included a questionnaire, VISA score and a vertical jump test. The VISA score and vertical jump test improved significantly in the study group. A limitation of this study was that no VAS score was used for the evaluation, even though it is a useful indica-tor of pain relief. Also in this study a short follow-up time was used and the number of patients was only 20. Taunton et al concluded that ESWT treatment could be of value as an additional treatment to other conservative therapies, like eccentric training.28

Wang et al (2007) evaluated the efficiency and safety of ESWT treatment for patellar ten-dinopathy. In a randomised controlled trial they compared one focused ESWT treatment of 0.18 mJ/mm2 with the results of conservative treatment. This study consisted of 27 patients (30 tendons) in the study group and 23 patients (24 tendons) in the control group. After 1, 3, 6, 12, 24 and 36 months VISA and VAS scores, functional improvement and ultrasonographic examination of the patellar tendon were evaluated. There was a sig-

Figure 6.2. Delphi score24

Delphi score

1. Treatment allocation a. Was a method of randomisation performed? (Yes/No/Don’t know) b. Was the treatment allocation concealed? (Yes/No/Don’t know)

2. Were the groups similar at baseline re garding the most important prognostic indicators? (Yes/No/Don’t know)

3. Were the eligibility criteria sp ecified? (Yes/No/Don’t know) 4. Was the outcome assessor blinded? (Yes/No/Don’t know) 5. Was the care provider blinded? (Yes/No/Don’t know) 6. Was the patient blinded? (Yes/No/Don’t know) 7. Were point estimates and measures of varia bility presented for the primary outcome

measures? (Yes/No/Don’t know) 8. Did the analysis include an intention-to-treat analysis? (Yes/No/Don’t know)

Figure 2: Delphi score23

72 Chapter 6

nificant improvement in patients who had been treated with ESWT. They showed func-tional improvement and both the VAS and the VISA scores improved. Ultrasonographic examination revealed a significant increase in vascularisation. There were no serious side effects or complications. According to Wang et al, this study had some limitations. The number of patients was small and the length of follow-up was relatively short, although the length of follow-up of this study was the largest of all seven studies included. The functional improvement of the knee was assessed subjectively on the performance of daily activities, including sports participation. Despite these limitations, they concluded that ESWT was more effective and safer than conservative treatment for patients with chronic patellar tendinopathy.15

In 2007 Vulpiani et al reported a prospective study on the treatment of jumper’s knee using ESWT. All included patients had a confirmed jumper’s knee for at least 3 months, with pain not responding to previous conservative treatment. All 73 patients (83 tendons) received from three to five focused ESWT treatments with an energy level of 0.08–0.44 mJ/mm2. Already 1 month after ESWT treatment a significant improvement in the aver-age VAS score was found, and the VAS scale improved further during follow-up. Ad-ditional evaluations after 1 month and in short-term (6–12 months), medium-term (13–24 months) and long-term (>24 months) periods showed satisfactory results in respectively 43%, 64%, 69% and 80% of the patients. However, 14 tendons were lost to follow-up. Clear limitations in this study were the study design, without a control group, and the impos-sibility of achieving a 100% patient recall. The study of Vulpiani et al showed positive ef-fects of ESWT treatment for patellar tendinopathy, so they concluded that the results were encouraging in light of the long-lasting improvement of the pain symptomatology.14

Discussion

All of the seven studies included in this review concluded that ESWT seems to be an effective treatment for patellar tendinopathy. It is a safe treatment as well because no serious side effects have been reported. Since there are many differences in the treatment protocols used, it would be inappropriate to attempt a quantitative meta-analysis on the effectiveness of ESWT for patellar tendinopathy, but based on these studies it can be estimated that in approximately 74.7% of patients ESWT treatment resulted in improve-ment of pain and knee function. The results should be interpreted with caution, though, since the quality of the studies is variable (Delphi score ranged from 2 to 7 out of a maximum of 9).24 Three studies6,14,26 were non-randomised, two studies had no control group,14,26 and one study had a retrospective design.6 Of the RCTs, one study compared ESWT treatment with conservative treatment,15 while in others placebo ESWT was ap-plied to the control group.24,27,28 One RCT was only single-blinded.25 Patients were blinded in only two studies. Further, in most studies small numbers of patients were used and the post-treatment follow-up time was generally short.6,14,15,25-28 Because of the aforemen-tioned limitations, which are also indicated by the fact that there were only two satisfac-tory Delphi scores, it is hard to draw firm conclusions about the effectiveness of ESWT for patellar tendinopathy.


6

Since no appropriate conservative or surgical treatments for this common injury have been described so far, we believe that the mainly positive results from these studies jus-tify further research into the role that ESWT can play in the management of athletes with patellar tendinopathy. Double-blind, randomised, controlled studies in larger patient groups and with sufficient follow-up time, for at least 3 years, using standardised treat-ment protocols are necessary to assess the true value of ESWT for patellar tendinopathy. Based on the available evidence in the literature it is impossible to recommend a specific ESWT treatment protocol. Hence comparative studies between different treatment strate-gies are also urgently needed. In this way, important questions with regard to number and frequency of treatments, energy level and method of shockwave application will be answered. There is no consensus either about the use of anaesthetics; it seems that their use is unnecessary. Almost all patients in this review received ESWT therapy without anaesthetics and they all tolerated it well. Research in the field of ESWT and tendinopathies is still hampered by the fact that both the pathophysiology of patellar tendinopathy and the exact working mechanism of ESWT have not been elucidated so far. The underlying pathology in patellar tendinopa-thy is considered to be a failed healing response due to a degenerative process resulting from excessive overload,8,13-15,21,23,26,28-30 rather than a prostaglandin-mediated inflammatory process.8,10 Neovascularisation is often found in patellar tendinopathy, and it has been hypothesised that tendon pain is caused by sensory nerves that grow into the tendon, causing a neurogenic inflammation and pain response.29 A further explanation of the pain in patellar tendinopathy could be the disturbance of nociceptive transmission in the nervous system, by means of changed levels of substance P (SP), glutamate and tyrosine hydroxylase (TH).29 Little is known about the working mechanism of ESWT. In animal studies2 it has been demonstrated that ESWT may have an impact on the nociceptive transmission in the nervous system and that it can cause dysfunction of peripheral, sen-sory nerve fibres, resulting in pain relief.16 ESWT probably has an influence on neovas-cularisation as well. Surprisingly, Wang et al found, along with the clinical improvement of their patients, a significant increase of vascularisation after ESWT treatment.15 They supposed the increased vascularity led to better tissue regeneration in tendinopathies through a better blood supply.15 This finding is in flat contradiction to the aforementioned theory about neurovascular structures and pain. A possible explanation could be that, due to the improvement in pain and function, patients became more active, resulting in increased vascularity.31 In athletes the degree of neovascularisation can also vary during the season,32 but no data on sport participation were given by Wang. In order to develop an effective ESWT treatment protocol for patellar tendinopathy it is crucial to elucidate the exact pathophysiology of patellar tendinopathy and to clarify the working mechanism of shockwaves on (pathological) tendon tissue and neovascularisation. Without more basic knowledge of these phenomena, ESWT will remain a controversial treatment.So far, ESWT has mainly been used to treat patients with a chronic severe patellar ten-dinopathy not responsive to other conservative treatments. The mean VISA score of the patients of the included studies was 47.8. In more than 50% of those studies, the mean duration of symptoms was over 6 months, and patients had mostly had several other treatments already. This may have negatively influenced the outcome of the studies. We

74 Chapter 6

believe that ESWT could be of help in an earlier, less severe stage of the disease as well. ESWT can potentially play a role in the management of tendon pain and therefore should be incorporated into a more comprehensive exercise-based rehabilitation programme.13,33 A more comprehensive programme also seems justified when we look at the VISA scores after treatment. Healthy athletes have a VISA score of around 95 points. In these studies the maximum VISA score was 92 and the average VISA score was 78. Peers et al showed that results of ESWT therapy equal the results of surgical treatment for patellar tendinop-athy; results showed a VISA score of respectively 83 and 70.6 Bahr et al compared surgi-cal treatment with eccentric training; results showed a VISA score of 70 for both groups.4 ESWT treatment seems just as effective as, or even more effective than, existing treatments for patellar tendinopathy, but a completely normal knee function is probably not feasible with monotherapy. A more comprehensive exercise-based rehabilitation programme could therefore help to achieve higher VISA scores.In conclusion, ESWT seems to be a safe and promising treatment for patellar tendinopathy. Because ESWT treatment seems to have a positive effect on pain and function, it could be part of a rehabilitation programme for this chronic overuse injury. However, based on the current knowledge it is impossible to recommend a specific treatment protocol. Further basic and clinical research into the working mechanism and effectiveness of ESWT for patellar tendinopathy is necessary.


6

References

1. Blazina ME, Kerlan RK, Jobe FW, Carter VS, Carlson GJ (1973). Jumper’s knee. Orthop Clin North Am; 4:665-78.


3. Zwerver J, Bredeweg SW. Prevalence of jumper’s knee among non-elite athletes from three different sports. Abstract book of the XXIX FIMS World Congress of Sports Medicine,Beijing, 2006 , 273. 2006.



6. Peers KH, Lysens RJ, Brys P, Bellemans J (2003). Cross-sectional outcome analysis of athletes with chronic patellar tendinopathy treated surgically and by extracorporeal shock wave therapy. Clin J Sport Med; 13:79-83.

7. Visnes H, Bahr R (2007). The evolution of eccentric training as treatment for patellar tendinopathy (jumper’s knee): a critical review of exercise programmes. Br J Sports Med; 41:217-23.

8. Alfredson H (2005). The chronic painful Achilles and patellar tendon: research on basic biology and treatment. Scand J Med Sci Sports; 15:252-9.


10. Khan KM, Cook JL, Kannus P, Maffulli N, Bonar SF (2002). Time to abandon the “tendinitis” myth. BMJ; 324:626-7.




14. Vulpiani MC, Vetrano M, Savoia V, Di Pangrazio E, Trischitta D, Ferretti A (2007). Jumper’s knee treatment with extracorporeal shock wave therapy: a long-term follow-up observational study. J Sports Med Phys Fitness; 47:323-8.


16. Chung B, Wiley JP (2002). Extracorporeal shockwave therapy: a review. Sports Med; 32:851-65.

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17. Ogden JA, Toth-Kischkat A, Schultheiss R (2001). Principles of shock wave therapy. Clin Orthop Relat Res;8-17.

18. Furia JP, Rompe JD (2007). Extracorporeal shock wave therapy in the treatment of chronic plantar fasciitis and achilles tendinopathy. Curr Opin Orthop;102-11.

19. Sems A, Dimeff R, Iannotti JP (2006). Extracorporeal shock wave therapy in the treatment of chronic tendinopathies. J Am Acad Orthop Surg; 14:195-204.

20. Peers KH (2003). Extracorporeal Shock Wave Therapy. Proefschrift KU Leuven.

21. Hsu RW, Hsu WH, Tai CL, Lee KF (2004). Effect of shock-wave therapy on patellar tendinopathy in a rabbit model. J Orthop Res; 22:221-7.

22. Maier M, Averbeck B, Milz S, Refior HJ, Schmitz C (2003). Substance P and prostaglandin E2 release after shock wave application to the rabbit femur. Clin Orthop Relat Res;237-45.

23. Peers KH (2003). Chronic tendinopathy. Proefschrift KU Leuven.

24. Verhagen AP, de Vet HC, de Bie RA, Kessels AG, Boers M, Bouter LM, Knipschild PG (1998). The Delphi list: a criteria list for quality assessment of randomized clinical trials for conducting systematic reviews developed by Delphi consensus. J Clin Epidemiol; 51:1235-41.

25. Vara F, Garzon N, Orthega N (2000). Treatment of patellar tendinitis woth local application of extracorporeal shock waves. Abstract from the 4th Congress of the International Society for Musculoskeletal Shock Wave Therapy Naples.

26. Lohrer H, Scholl J, Arentz S (2002). [Achilles tendinopathy and patellar tendinopathy. Results of radial shockwave therapy in patients with unsuccessfully treated tendinoses]. Sportverletz Sportschaden; 16:108-14.

27. Peers KH (2003). Extracorporeal Shock Wave Therapy in chronic patellar tendinopathy: a randomised double-blinded, placebo-controlled trial. Proefschrift KU Leuven.

28. Taunton K.M, Taunton J.E, Khan K.M (3 A.D.). Treatment of patellar tendinopathy with extracorporeal shockwave therapy. BC Medical Journal; 45:500-7.

29. Lian O, Dahl J, Ackermann PW, Frihagen F, Engebretsen L, Bahr R (2006). Pronociceptive and antinociceptive neuromediators in patellar tendinopathy. Am J Sports Med; 34:1801-8.

30. Tasto JP, Cummings J, Medlock V, Harwood F, Hardesty R, Amiel D (2003). The tendon treatment center: new horizons in the treatment of tendinosis. Arthroscopy; 19 Suppl 1:213-23.

31. Boesen MI, Koenig MJ, Torp-Pedersen S, Bliddal H, Langberg H (2006). Tendinopathy and Doppler activity: the vascular response of the Achilles tendon to exercise. Scand J Med Sci Sports; 16:463-9.


33. Alfredson H, Cook J (2007). A treatment algorithm for managing Achilles tendinopathy: new treatment options. Br J Sports Med; 41:211-6.

Chapter 7

The TOPGAME study: effectiveness of extracorporeal

shockwave therapy in jumping athletes with patellar

tendinopathy. Design of a randomised controlled trial

J. Zwerver E. Verhagen F. Hartgens

I. van den Akker-Scheek R.L. Diercks

BMC Musculoskelet Disord. 2010 Feb 8;11:28.

80 Chapter 7

Abstract

Background: Patellar tendinopathy is a major problem for many athletes, es-pecially those involved in jumping activities. Despite its frequency and negative impact on athletic careers, no evidence-based guidelines for management of this overuse injury exist. Since functional outcomes of conservative and surgical treatments remain suboptimal, new diagnostic and therapeutic strategies have to be developed and evaluated. Extracorporeal shockwave therapy (ESWT) ap-pears to be a promising treatment in patients with chronic patellar tendinopa-thy. ESWT is most often applied after the known conservative treatments have failed. However, its effectiveness as primary therapy has not been studied in athletes who keep playing sports despite having patellar tendon pain.

Aim: The aim of this study is to determine the effectiveness of ESWT in ath-letes with patellar tendinopathy who are still in training and competition.

Methods/design: The TOPGAME-study (Tendinopathy of Patella Groningen Amsterdam Maastricht ESWT) is a multicentre two-armed randomised con-trolled trial with blinded participants and outcome assessors, in which the ef-fectiveness of patient-guided focussed ESWT treatment (compared to placebo ESWT) on pain reduction and recovery of function in athletes with patellar tendinopathy will be investigated. Participants are volleyball, handball and basketball players with symptoms of patellar tendinopathy for a minimum of 3 to a maximum duration of 12 months who are still able to train and compete. The intervention group receives three patient-guided focused medium-energy density ESWT treatments without local anaesthesia at a weekly interval in the first half of the competition. The control group receives placebo treatment. The follow-up measurements take place 1, 12 and 22 weeks after the final ESWT or placebo treatment, when athletes are still in competition. Primary outcome measure is the VISA-P (Victorian Institute of Sport Assessment - patella) score. Data with regard to pain during function tests (jump tests and single-leg decline squat) and ultrasound characteristics are also collected. During the follow-up pe-riod participants also register pain, symptoms, sports participation, side effects of treatment and additional medical consumption in an internet-based diary.

Discussion: The TOPGAME-study is the first RCT to study the effectiveness of patient-guided ESWT in athletes with patellar tendinopathy who are still in training and competition.

Trial registration: Trial registration number NTR1408.

Design of the TOPGAME study 81

7

Background

Patellar tendinopathy (’jumper’s knee’) is a clinical condition of gradually progressive ac-tivity-related pain at the insertion of the patellar tendon at the apex patellae.1 Prolonged repetitive stress of the knee-extensor apparatus can lead to this common overuse tendi-nopathy in athletes from different sports.2 The overall prevalence of patellar tendinopa-thy among elite and non-elite athletes is high and varies between 3 and 45%.3,4 In sports characterised by high demands on speed and power for the leg extensors, such as vol-leyball and basketball a prevalence of respectively 44.6% and 31.9% has been reported.3 In sports medicine centres patellar tendinopathy is one of the leading causes for athletes to consult physicians or physical therapists. Patellar tendinopathy often contributes to the decision to quit an athletic career and also causes mild but long-lasting symptoms after an athletic career.5 The high prevalence, impact on sports performance, and chronic nature of the condition all mean that in some jumping sports, patellar tendinopathy may cause at least as much impairment in athletic performance as acute knee injuries.3

There is no consensus on what is the most appropriate treatment for patellar tendinopa-thy.6,7 Several conservative treatment modalities (e.g. physical therapy, anti-inflammatory medication, rest, exercise) and different surgical procedures for treatment of patellar ten-dinopathy have been described.6-9 Overall, they have not been proven to be highly suc-cessful in relieving symptoms to such a degree that athletes can continue to participate in their sport at their full potential.8 New treatment modalities for patellar tendinopathy have recently been introduced, based on the finding that the pathology underlying chron-ic (patellar) tendinopathies is not inflammatory tendinitis but a degenerative tendinosis due to a failed healing response.10

In the last few years, extracorporeal shockwave therapy (ESWT) has also been used for the treatment of patellar tendinopathy. It seems to be a safe and promising treatment for patellar tendinopathy.11 In most of the research on ESWT treatment for patellar tendi-nopathy to date, patients have been recruited in a referral-based specialist care setting. Moreover, ESWT is often only applied when other treatments have already failed. This means that most patients included in these studies have serious, chronic problems, gener-ally to the extent that they had to stop sports participation entirely, or at least reduce their level of sports participation significantly. One can presume that patients in this stage have a decreased healing tendency and are possibly less responsive (more resistant) to all treatment modalities. To our knowledge, the effectiveness of ESWT has not been system-atically investigated in athletes who have early symptomatic patellar tendinopathy and are still actively competing. The aim of the TOPGAME study is to determine the effectiveness of ESWT on pain, symptoms and function, in athletes with patellar tendinopathy at an early stage of the disease who are still in training and competition.

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Methods/design

DesignThe TOPGAME study (Tendinopathy Of Patella Groningen Amsterdam Maastricht ESWT) is a multicentre randomised controlled trial with blinded participants and outcome assessors, using a two-group repeated measures design with a treatment period of 2 weeks and a 22 week follow-up. Participants are randomized into an intervention ESWT group or a placebo control group. Recruitment of participants for the TOPGAME trial takes place in May-November 2008 and data collection starts in September 2008

Ineligible- Fail inclusion criteria - Meet exlusion criteria

Phone or e-mail screening Invitation for physical screening

Informed consentBaseline measurements

Physical screening by sports medicine physician



Web-based screening for athletes with high likelihood for patellar tendinopathy (Questionnaire for basketball, handball and volleyball players)

Randomisation at team level

3 ESWT treatments at weekly interval

Registration of athletic activity and concurrent treatment in web based log

Allocation to intervention (ESWT) group

3 sham-ESWT treatments (placebo) at weekly interval

Registration of athletic activity and concurrent treatment in web based log

Allocation to control (placebo) group

In season evaluations one, twelve and twenty-two weeks after ESWT or placebo treatment

Figure 7.1. TOPGAME Trial Profile. The Trial profile of the TOPGAME study.


7

(first half of the competition season). The ESWT and placebo treatments start in October 2008. After three ESWT or placebo treatments, the follow-up measurements take place at 1, 12 and 22 weeks after the final treatment, when athletes are still in competition. The trial profile is shown in Figure 7.1. The study design, procedures and informed consent procedure were approved by the Medical Ethics Committee (Number 2008/052) of the University Medical Center Groningen (UMCG), the Netherlands. All participants have to provide written informed consent.

Study populationRecruitment of the participants is facilitated by the Dutch Basketball Association (Neder-landse Basketbalbond, NBB), Dutch Handball Association (Nederlands Handbalverbond, NHV) and the Dutch Volleyball Association (Nederlandse Volleybalbond, NEVOBO). Through both an advertisement on their website and an e-mail sent to all their athletes (aged 18-35) and the coaches of the club teams, attention is drawn to the TOPGAME-study. Recruitment is further assisted by advertisements in local, regional and national newspapers and by advertising at tournaments and games. All athletes are invited to fill out a questionnaire on sports participation and knee prob-lems (including a pain map) on a specially designed website http://www.topgamestudie.nl. They are also asked for their willingness to participate in the study. After this ques-tionnaire-based screening, participants with a high likelihood of having patellar tendi-nopathy are contacted by mail or phone and sent written information about the study. If they still want to participate, they receive an invitation for a consultation by one of the two sports medicine physicians of the study (FH, JZ) at a sports medicine practice in their neighbourhood. The sports medicine physicians examine all the participants and clinically establish the diagnosis of patellar tendinopathy using the criteria described below. Eligible participants are included in the study after informed consent. Thereafter, baseline measurements are carried out and athletes will be randomized to either the inter-vention (ESWT) group or the control (placebo) group.

Inclusion and exclusion criteriaMale and female basketball, handball and volleyball players with the following criteria are eligible for inclusion: 1. History of knee pain in the patellar tendon or its patellar or tibial insertion (pointed

out in an anatomical drawing of the knee) in connection with training and competi-tion.

2. Symptoms for over three months in the actual season or in the second half of the previous season (January-May 2008) (to exclude acute inflammatory tendon prob-lems and de novo partial ruptures).

3. Age 18-35 years (to reduce chances of osteochondrotic diseases like Sinding-Larsen-Johanson, Osgood-Schlatter and osteoarthrosis).

4. Palpation tenderness at the corresponding painful area.5. VISA-P score < 80. The VISA-P (Victorian Institute of Sport Assessment - patella)

score is a short questionnaire measuring the severity of patellar tendinopathy by assessing pain, function and ability to play sports.12,13

Athletes are excluded if they suffer from acute knee or acute patellar tendon injuries, have

84 Chapter 7

chronic joint diseases or have signs or symptoms of other (co-)existing knee pathologies. Athletes who use drugs with a putative effect on patellar tendinopathy in the last year on daily basis (e.g. non-steroid anti-inflammatory drugs, fluorquinolones) or use anticoagu-lants, and athletes who had knee surgery or injection therapy with corticosteroids in the last preceding three months are also excluded. Athletes with contraindications for ESWT treatment (pregnancy, malignancy, coagulopathy) are also excluded from the study.

RandomizationVolleyball, handball and basketball players with patellar tendinopathy are allocated ran-domly and blinded to an intervention group (patient-guided ESWT) or a control group (placebo treatment) by an independent statistician (EV) who is blinded for any baseline characteristics of the participants. Randomisation is performed before the first treatment by means of a computer-generated randomization list (SPSS 16, Chicago, USA). The ran-domization procedure takes place at team level, resulting in players from the same teams being allocated to the same group. While the different treatment methods within the study groups potentially have various immediately noticeable effects on the subjects (e.g. level of pain), this method of randomisation is chosen to keep the treatment group blinded to the subjects, and to avoid spill-over of the intervention. The independent physical thera-pists who administer the ESWT or placebo treatment are informed by the statistician about the group allocation. Group allocation is concealed from the athletes and the out-come assessor at all times during the trial.

InterventionESWT treatment and placebo treatments will be given by five independent physical ther-apists at four different locations across the Netherlands.

ESWT treatmentThe physical therapist will explain the treatment procedure to the athlete and will pal-pate the patellar tendon to find the most painful spot. ESWT is applied according to the guidelines of the International Society for Musculoskeletal Shockwave Therapy (ISMST) using a piezo-electric ESWT device (Piezowave, Wolf GmbH, Knittlingen, Germany). This will be administered in three sessions at one-week intervals using 2000 impulses at a frequency of 4 Hz. The energy flux density will be titrated according to individual pain tolerance up to a possible maximum of 0.58 mJ/mm2 (level 20). Treatment will start at level 5 (0.1 mJ/mm2). The athlete will be told that treatment can be painful but that there is inter-individual variability in pain perception. After every 100 impulses the physi-cal therapist will ask the athlete, if he/she can tolerate the treatment. If he/she can, the physical therapist will increase the energy flux density by one level, up to the aforemen-tioned maximum level. A transmission gel will be applied between the applicator and the focussing pad as well as between the focussing pad and the skin of the patient to optimise shockwave transmission to the patient. No local anaesthesia will be used, since Rompe and colleagues demonstrated that repetitive application of shockwaves is more effective without than with local anaesthesia.14 The athlete will be in supine position with an extended knee and shockwaves will be focused on the painful zone in the tendon or insertion. The inferior pole of the patella will be tilted to focus on the dorsal insertion of


7

the patellar tendon as well. The aforementioned treatment protocol was chosen based on our previous experience with ESWT application in patients with patellar tendinopathy (submitted). All patients in the pilot study tolerated this procedure well without adverse complications.

Placebo treatmentThe treatment procedure for the athletes in the control group is nearly the same. Placebo treatment will be administered using the same device. The transmission gel will be ap-plied between the focussing pad and skin of the patient, but not between applicator and focussing pad. This is invisible for the athletes, since it is inside of the device. In this way shockwaves are not or hardly conducted. Measurements of energy density provided by the manufacturer for this placebo set-up revealed negligible or only very low energy densities of less than 0,03mJ/mm2 (Wolf GmbH, Knittlingen, Germany). The athlete will also be told that treatment can be painful but that there is inter-individual variability in pain perception. By pressing the applicator with focussing pad to the painful spot, athletes will also experience some pain. The physical therapist will also ask after every 100 impulses if the athlete can toler-ate the ESWT treatment, but energy flux density will not increase during the treatment. Athletes in the placebo group will also hear the repetitive impulses generated by the ESWT-device, yet will be unaware of the dosage administered.

Concurrent sports participation and medical treatmentNo restrictions will be given for both groups with regard to sport participation or concur-rent medical treatment. If the athlete will experience an increase in pain in the first 48 hours after treatment he/she will be advised to take paracetamol up to a maximum dose of 3 dd 1000 mg for pain relief.

Measurements BaselineAfter informed consent the following baseline measurements will be carried out:

Baseline questionnaireThe baseline questionnaire consists of three parts. Part 1 covers demographic variables such as name, address, age, gender, and e-mail address. Sports participation will be as-sessed in part 2 by using questions concerning type and level of sport and mean hours of sports participation and sport history. Information about medical history, knee injuries and previous medical treatment will be collected in the third part of the questionnaire. VISA-P questionnaireThe primary outcome of the TOPGAME study is the self-reported VISA-P score.12 The VISA-P score is a simple, reliable instrument for measuring the severity of patellar ten-dinopathy and is sensitive to small changes in symptoms. It was specifically designed for patellar tendinopathy, rating pain, symptoms, simple test of function and the ability to play sports. Six of the eight questions are scored on a scale from 0 to 10 points, with 10 representing optimal health. The maximum VISA score for an asymptomatic athlete

86 Chapter 7

is 100 points. Validity and reliability of the Dutch translation of the VISA-P score have been demonstrated recently.13

VAS painSecondary outcome parameters are ratings of pain on a Visual Analogue Scale (VAS) dur-ing activities of daily living (ADL) and sports, and during functional tests like maximal jumping tests, triple hop test and the single leg decline squat (SLDS); the latter test, in which the athlete performs a single-leg squat to 60° of knee flexion on a 25° decline board ten times, was designed to preferentially load the patellar tendon.15,16

UltrasoundGreyscale ultrasound and Power/Colour Doppler characteristics of the patellar tendon (hypo-echogenity, diameter, calcifications, and degree of neovascularisation) will be col-lected by an experienced radiologist.

Follow-upFollow-up measurements for VISA-P and the VAS pain assessments will be carried out at 1, 12 and 22 weeks after the final treatment, when athletes are still in competition. Side effects and adverse reactions/events and the rate of overall treatment satisfaction will also be recorded. At 22 weeks after final treatment, ultrasound characteristics will be collected by the same experienced radiologist who is blinded to the athletes’ group allocation. Further both groups of athletes will be recording their athletic activities and concurrent medical treatment on a weekly basis, using a web-based diary.

Sample sizeSample size is calculated based on the VISA-P score. From previous investigations a baseline score of 64 points is expected in symptomatic athletes (95 points in athletes without patellar tendinopathy), with an SD of 19 points (2). (To our knowledge no data are available that describe the SD of the difference between the baseline and 6 month VISA-score.) A 15-point difference in the VISA score between the treatment and placebo is considered to be clinically relevant. To detect a difference of 15 points on the VISA scale with an SD of 19, a power of 90% and an alpha of 5%, 34 subjects per group are needed.The proposed treatment protocol without local anaesthesia and with patient-guided dos-age (for pain tolerance) is chosen based on our previous experience with ESWT applica-tion in patients with patellar tendinopathy (J. Zwerver, submitted). All patients tolerated this procedure well without adverse complications; therefore we do not expect a higher-than-normal drop-out rate of athletes due to pain during the treatment. Assuming a drop-out rate of about 20% this would mean that a total of 86 subjects are required at baseline (43 in each group).

Statistical analysesDescriptive statistics (means and standard deviations, numbers and percentages) will be used to describe the characteristics of the intervention and control group and the outcome variables at the three measurement points. To evaluate potential group differences at the


7

start of the study, baseline values will be analysed for differences between intervention group and control group. The effect of the ESWT treatment will be assessed using multi-level analysis. The multilevel analysis will be used to determine whether there is a differ-ence on the primary and secondary outcome variables between the two groups over time. This statistical technique takes into account the dependency of observations of different subjects. Analyses will be adjusted for gender, age, type of sport, and baseline values of any other post hoc confounders. Analyses will be performed following the ‘intention to treat’ principle. Differences will be considered statistically significant at p < 0.05. All analyses will be done using SPSS version 16 (SPSS, Chicago, USA).

Discussion

Despite its frequency and impact on athletic careers, and decades of research notwith-standing, management of patellar tendinopathy remains frustrating and unpredictable for both athletes and clinicians. ESWT appears to be a promising treatment method in pa-tients with chronic patellar tendinopathy.11 Up to now, only studies have been published in which ESWT has been used for the treatment of recalcitrant patellar tendinopathy in athletes who had several conservative treatments before and were finally referred to a sports medicine department for ESWT.11 However, the effectiveness of ESWT has not been studied in the large group of athletes who continue sports participation with an early or mild symptomatic patellar tendinopathy. The TOPGAME study is the first RCT to study the effectiveness of patient-guided piezo-electrically generated ESWT in athletes with patellar tendinopathy who are still in training and competition. To our knowledge, it is also the first study that takes into account the training and competition load of the athletes using a web-based log.This study will contribute to a better understanding of the effectiveness of ESWT as treatment for athletes with patellar tendinopathy who are still able to train and compete. By treating them at an early phase, we can get relevant information on whether it is possible to reverse or stop the progression of patellar tendinopathy, thereby preventing chronic impairment of athletic performance, work and daily activities.

Conclusions

The TOPGAME study is the first RCT to evaluate the effectiveness of patient-guided ESWT in athletes with early-phase symptomatic patellar tendinopathy who are still in training and competition.

Acknowledgements This study was funded by the Netherlands Organisation for Health Research and development

(ZonMW), grant number 750.20.010.

88 Chapter 7

List of abbreviationsTOPGAME: Tendinopathy of Patella Groningen Amsterdam Maastricht ESWT; ESWT: Extracor-

poreal Shockwave Therapy; RCT: Randomised Controlled Trial; NBB: Nederlandse Basketbalbond

(Dutch Basketball Association); NHV: Nederlands Handbalverbond (Dutch Handball Association);

NEVOBO: Nederlandse Volleybalbond (Dutch Volleyball Association); VISA-P: Victorian Institute of

Sport Assessment - patella.


7


North Am; 4:665-78.



4. Zwerver J, Bredeweg S. Prevalence of jumper’s knee among non-elite athletes from three different sports. Abstract book of the XXIX FIMS World Congress of Sports Medicine,Beijing, 2006 , 273. 2006.







11. van Leeuwen MT, Zwerver J, Akker-Scheek I (2009). Extracorporeal shockwave therapy for patellar tendinopathy: a review of the literature. Br J Sports Med; 43:163-8.



14. Rompe JD, Meurer A, Nafe B, Hofmann A, Gerdesmeyer L (2005). Repetitive low-energy shock wave application without local anesthesia is more efficient than repetitive low-energy shock wave application with local anesthesia in the treatment of chronic plantar fasciitis. J Orthop Res; 23:931-41.



Chapter 8

No effect of extracorporeal shockwave therapy on patellar

tendinopathy in jumping athletes during the competitive season: a

randomised clinical trial

J. Zwerver F. Hartgens E. Verhagen

H. van der Worp I. van den Akker-Scheek

R.L. Diercks

Accepted for Am J Sports Med.

92 Chapter 8

Abstract

Background: Patellar tendinopathy (PT) is a common overuse injury among jumping athletes. No evidence-based treatment guidelines exist. Extracorporeal shockwave therapy (ESWT) appears to be a promising treatment but its effec-tiveness has not been studied in athletes with PT who have symptoms for 3 to 12 months and are still playing.

Aim: Aim of the TOPGAME study was to determine the effectiveness of ESWT on pain, symptoms and function in athletes with early symptomatic pa-tellar tendinopathy who are still in training and competition.

Study design: Randomised controlled clinical trial

Methods: Athletes playing volleyball, basketball or handball with PT for 3 to 12 months were randomised into the ESWT or placebo group during the first half of the season. The ESWT group received 3 ESWT treatments while the placebo group received sham ESWT. In-season follow-up measurements were 1, 12 and 22 weeks after treatment. Primary outcome was severity of PT deter-mined with the VISA-P questionnaire. Secondary outcome was pain on a VAS during ADL and sports and after performance of functional tests. Multilevel analyses were performed to determine differences between groups over time.

Results: 127 symptomatic athletes were invited to participate; 62 were eligible, gave consent and were randomised into the ESWT (n=31) or placebo group (n=31). Mean VISA-P scores before and 1, 12 and 22 weeks after treatment were 59.4 (±11.7), 66.8 (±16.2), 66.7 (±17.5) and 70.5 (±18.9) for the ESWT group and 62.4 (±13.4), 66.3 (±19.0), 68.9 (±20.3) and 72.7 (±18.0) for the placebo group. There was a significant effect for time (p<0.01) but no treatment x time interac-tion effect (p=0.82). Secondary outcome measures showed the same.

Conclusions: ESWT as monotreatment during the competitive season has no benefit over placebo treatment in the management of actively competing jumping athletes with patellar tendinopathy who have mild symptoms for less than 12 months.

The TOPGAME study; no effect of ESWT 93

8

Background

Patellar tendinopathy (“jumper’s knee”) is a clinical condition of gradually progres-sive activity-related pain of the patellar tendon, most commonly at the insertion at the apex patellae.1 Prolonged repetitive stress of the knee extensor apparatus can lead to this common overuse tendinopathy in athletes from several different sports.2 The overall prevalence of patellar tendinopathy among elite and non-elite athletes is high and varies between 3 and 45%.3,4 In sports characterized by high demands on speed and power for the leg extensors, such as volleyball and basketball, a prevalence of 44.6% and 31.9% respectively has been reported.4 Patellar tendinopathy is one of the leading causes for athletes to consult physicians or physical therapists in sports medicine centres. It often contributes to the decision to quit an athletic career and also causes mild yet long-lasting symptoms after such a career.5 the overall high prevalence, the impact on sports perfor-mance and the chronic nature of the condition show that in some jumping sports patellar tendinopathy can have the same health impact as acute knee injuries.4

There is no consensus on what is the most appropriate treatment for patellar tendinopa-thy.6,7 Several conservative treatment modalities (e.g. physical therapy, anti-inflammatory medication, rest, exercise) and different surgical procedures have been described.6-9 Over-all, they have not been proven to be highly successful in relieving symptoms to such a degree that athletes can continue to participate in their sport at their full potential.8 New treatment modalities for patellar tendinopathy have recently been introduced, based on the finding that the pathology underlying chronic (patellar) tendinopathies is not inflam-matory tendinitis but a degenerative tendinosis due to a failed healing response.10 Extracorporeal shockwave therapy (ESWT) is one of these new treatments which might enhance regeneration. In the last few years ESWT has also been used to treat patellar ten-dinopathy, and seems to be a safe and promising treatment for this condition.11 In most of the research on ESWT treatment for patellar tendinopathy, patients have been recruited on a referral-based specialist care setting. Moreover, ESWT is often only applied when other treatments have already failed. This means that most patients included in these studies have serious, chronic problems, generally to such extent that they had to stop playing sports entirely, or at least reduce their level of sports participation significantly. One can presume that patients in this stage have a decreased healing tendency and are possibly less responsive (more resistant) to all treatment modalities. To our knowledge, the effectiveness of ESWT has not been systematically investigated in athletes who have early symptomatic patellar tendinopathy and are still actively competing. The aim of the current study was therefore to determine the effectiveness of ESWT on pain, symptoms and function, in athletes with patellar tendinopathy whose symptoms have lasted between 3 and 12 months and who are still in training and competition.

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Methods/design

DesignThe TOPGAME study (Tendinopathy Of Patella Groningen Amsterdam Maastricht ESWT) was a multi-centre randomised controlled trial with blinded participants and out-come assessors, using a two-group repeated measures design with a treatment period of 2 weeks and 22 weeks of follow-up (trial number NTR1408). We tested the hypothesis that ESWT is more effective than placebo ESWT in relieving pain and symptoms and improving function in athletes with early symptomatic patellar tendinopathy who are still in training and competition. An extensive description of the design of the TOPGAME study is published elsewhere.12 The study design, procedures and informed consent pro-cedure were approved by the Medical Ethics Committee (Number 2008/052) of University Medical Center Groningen (UMCG), the Netherlands.

RecruitmentRecruitment of participants for the TOPGAME study took place in May-November 2008 and was facilitated by the Dutch Basketball, Handball and Volleyball associations, who sent a generic informative e-mail to all their registered athletes (aged 18-35). Additional attention was also drawn to the TOPGAME study through advertisements in newspa-pers and websites and at tournaments. Athletes were invited to fill out an internet-based questionnaire on sports participation and current knee complaints, and were also asked if they would be willing to participate in the study. Athletes with a high likelihood of hav-ing patellar tendinopathy based on a description of their symptoms and the localization on a pain map received written information about the study and were contacted by mail or phone. They were invited for a consultation by one of the two sports medicine physi-cians of the study (FH, JZ), who examined all the athletes and clinically established the diagnosis of patellar tendinopathy using the criteria described below.

ParticipantsMale and female basketball, handball and volleyball players aged 18-35 who met the fol-lowing criteria were included:

History of knee pain in the patellar tendon or its patellar or tibial insertion 1. in connection with training and competition, and palpation tenderness at the corresponding painful area.Symptoms for 3 to 12 months in the current season or in the second half of the 2. previous season (January–May 2008).VISA-P score < 80. The VISA-P (Victorian Institute of Sport Assessment - 3. Patella) score is a short questionnaire measuring the severity of patellar tendi-nopathy by assessing pain, function and ability to play sports.13

No imaging studies were done to confirm the clinical diagnosis since previous studies have demonstrated that, although ultrasound and MRI can increase the likelihood of the diagnosis, they are not conclusive.14,15 Athletes were excluded if they suffered from acute knee injuries or other (co-)existing knee pathology, used non-steroid anti-inflammatory drugs or fluoroquinolones, had knee surgery or injection therapy with corticosteroids in


8

the preceding three months or had contraindications for ESWT treatment (pregnancy, malignancy, use of anticoagulants, coagulopathy).

RandomisationParticipants were allocated randomly and blinded to an intervention group (patient-guid-ed ESWT) or a control group (placebo treatment) by an independent statistician (EV) who was blinded for any baseline characteristics of the participants. Randomisation was done before the first treatment by means of a computer-generated randomisation list (SPSS 16, Chicago). The randomisation procedure took place at the team level, resulting in players from the same teams being allocated to the same group. While the different treatment methods within the study groups potentially have various immediately noticeable effects on the subjects (e.g. level of pain), this method of randomisation was chosen to keep the treatment allocation blinded to the subjects and to avoid spill-over of the intervention. The independent physical therapists who administered the ESWT or placebo treatment were informed by the statistician about the group allocation. Group allocation was con-cealed from the athletes and the outcome assessor at all times during the trial. To evaluate athlete blinding, athletes were asked at final follow-up to indicate which treatment they believed they had received (ESWT, placebo ESWT or don’t know).

InterventionESWT treatment and placebo treatments were given by five experienced and indepen-dent physical therapists at four different (sports) medicine centres across the Netherlands. They received a specific training on how to apply the ESWT and placebo ESWT before the start of the study. In case of bilateral symptoms the worst knee was evaluated and treated.

ESWT treatmentESWT was administered in three sessions at one-week intervals using a piezoelectric ESWT device (Piezowave, Wolf GmbH, Knittlingen, Germany). After explaining the treatment procedure to the athlete, the physical therapist palpated the patellar tendon to find the most painful spot. At this painful zone 2000 impulses at a frequency of 4 Hz were administered. The energy flux density was titrated according to individual pain tolerance up to a possible maximum of 0.58 mJ/mm2 (level 20). Treatment started at level 5 (0.1 mJ/mm2). The athlete was told that treatment could be painful but that there is inter-individ-ual variability in pain perception. After every 100 impulses the physical therapist asked the athlete, if he/she tolerated the treatment. If so, the therapist increased the energy flux density by one level, up to the aforementioned maximum level. A transmission gel was applied between the applicator and the focusing pad (before the athlete entered the room) as well as between the focusing pad and the skin of the patient to optimize shockwave transmission to the patient. Pads with a focus of 5 or 10 mm were used, depending on the athlete’s body stature. No local anaesthesia was used, since Rompe and colleagues demonstrated that repetitive application of shockwaves is more effective without than with local anesthesia.16 The athlete was in supine position with a slightly flexed knee and shockwaves were focused on the painful zone in the tendon or insertion. The inferior pole of the patella was tilted to focus on the dorsal insertion of the

96 Chapter 8

patellar tendon as well. This treatment protocol was chosen based on our previous experi-ence with ESWT application in patients with chronic patellar tendinopathy.17

Placebo treatmentThe treatment procedure for the athletes in the placebo group was the same, except that no transmission gel was applied between applicator and focusing pad. In this way shock-waves are not or hardly conducted. Measurements of energy density provided by the manufacturer for this placebo set-up revealed negligible or only very low energy densities of less than 0.03 mJ/mm2 (Wolf GmbH, Knittlingen, Germany). The physical therapist gave the same instructions and by pressing the focusing pad to the painful spot athletes experienced some pain; the athletes in the placebo group also heard the repetitive im-pulses of the ESWT device and even saw the physical therapist adjusting the level after every 100 impulses, yet were unaware of the dosage administered.

Concurrent sports participation and medical treatmentNo restrictions were given for either group with regard to sports participation or concur-rent medical treatment. If the athlete experienced an increase in pain in the first 48 hours after treatment he/she was advised to take acetaminophen up to a maximum dose of 3 dd 1000 mg for pain relief.

Measurements BaselineCollection of baseline data started in September 2008 and continued during the first half of the competition season until December 2008. After informed consent the following baseline measurements were carried out:

Baseline questionnaireThe baseline questionnaire covered demographic variables, hours of sports participation and information about the injury and previous medical treatment.

VISA-P questionnaireThe primary outcome of the TOPGAME study was the self-reported VISA-P score.13 The VISA-P score is a simple, reliable instrument for measuring the severity of patellar tendinopathy and is sensitive to small changes in symptoms. It was specifically designed for patellar tendinopathy, rating pain, symptoms, simple test of function and the ability to play sports. Six of the eight questions are scored on a scale from 0 to 10 points, with 10 representing optimal health. The maximum VISA score for an asymptomatic athlete is 100 points. Validity and reliability of the Dutch translation of the VISA-P score have been demonstrated recently.18

VAS painSecondary outcome parameters were ratings of pain on a Visual Analogue Scale (VAS) during activities of daily living (ADL) and sports, and after performance of functional tests: maximal jumping test, triple-hop test and single-leg decline squat (SLDS). In the first test athletes performed a maximal countermovement jump three times using their


8

left or right leg or both legs, and pain was recorded immediately after. In the triple-hop test athletes performed three hops with both their right and left leg; total distance and pain were recorded. The SLDS test, in which the athlete performs a single-leg squat to 60° of knee flexion on a 25° decline board, was designed to preferentially load the patel-lar tendon. It was performed once, then pain was assessed and then nine consecutive single leg decline squats were done, followed by pain assessment.19,20 Assessors of the functional tests were medical and physical therapy students who had received specific training before the start of this study and who were unaware of the athletes’ group al-location. Athletes were instructed on how to perform the functional tests and there was one practice session before the real measurements took place.

Follow-upAll measurements were repeated 1, 12 and 22 weeks after the final treatment session, when athletes were still in competition. Side effects and adverse reactions/events as well as rate of overall treatment satisfaction were also recorded. Further, all athletes recorded their athletic activities and concurrent medical treatment on a weekly basis, using a web-based diary. Athletes were also asked if they had noticed improvement of symptoms and if they would recommend their treatment to family and friends.

Sample sizeSample size was calculated based on the VISA-P score. From a previous investigation a baseline score of 64 points was expected in symptomatic athletes (95 points in athletes without patellar tendinopathy), with a SD of 19 points.30 A 15-point difference in VISA scores between the treatment and placebo groups was considered to be clinically relevant. To detect a difference of 15 points on the VISA scale with an SD of 19, a power of 90% and an alpha of 5%, 34 subjects per group were needed.

Statistical analysesDescriptive statistics (means and standard deviations, numbers and percentages) were used to describe the characteristics of the intervention and placebo groups and the outcome variables at the four measurement points. Multilevel analysis was used to assess the effect of the ESWT treatment and to determine whether there was a dif-ference on the primary and secondary outcome variables between the two groups over time. This statistical technique takes into account the dependency of observa-tions within subjects. Analyses were performed following the intention-to-treat prin-ciple (last observation carried forward). Differences were considered statistically sig-nificant at p < 0.05. All analyses were done using SPSS version 16 (SPSS, Chicago).

98 Chapter 8

11 Did not react on invitation

50 did not meet the inclusion criteria: 27 duration of symptoms 17 other or concomitant knee problems 3 previous ESWT treatment 2 VISA > 80 1 pregnant

3 Failed to attend baseline measurements

Contacted, invitation for participation N=127

Appointment for baseline measurements N=116

Baseline measurements N=113

1 withdrawal because of travelling time

Internet based questionnaire for basketball, handball and volleyball players Screening for athletes with high likelihood for patellar tendinopathy

Randomisation at team level N=62

3 ESWT treatments N=30 1 withdrawal because of travelling time

Allocated to ESWT group N=31

3 placebo treatments N=28 1 withdrawal because of travelling time 1 withdrawal for unclear reasons 1 withdrawal because of other injury

Followed up at Week 1 N = 30Week 12 N = 30Week 22 N = 30

Included in intention to treat analysis N=31

Included in intention to treat analysis N=31

Followed up at Week 1 N = 27 1 lost to follow up for unclear reasonWeek 12 N = 27 Week 22 N = 27

Allocated to placebo group N=31

Figure 8.1. Flow of participants throughout the trial and reasons for participant withdrawal


8

Results

The flow of participants through the trial and reasons for participant withdrawal are shown in Figure 8.1. Of the 127 athletes who were contacted after completing the internet-based questionnaire, 63 met the inclusion criteria. One athlete decided not to participate because of travelling time, therefore in the end a total of 62 participants were randomised to either ESWT or placebo treatment.Fifty-seven participants (92%) completed all treatments and measurements. The five who dropped out of the study had similar characteristics and baseline results compared to those with complete follow-up. There were no significant baseline differences between the ESWT and placebo groups for demographic and clinical characteristics (Table 8.1). Mean duration of symptoms was 7.3 ± 3.6 and 8.1 ± 3.8 months, respectively. Before the start of the study, 58% of the athletes in both groups had tried to reduce their symptoms by doing stretching exercises, reducing their training load and/or using a patellar strap. All patients tolerated the treatment procedure well without side effects or adverse com-plications. The averages of mean and maximum energy density applied were 0.25 ± 0.07 mJ/mm2 and 0.42 ± 0.17 mJ/mm2, respectively.

Primary outcome measureMean VISA-P scores before and 1, 12 and 22 weeks after treatment are summarized in Table 8.2. The mean VISA-P scores for the ESWT and placebo group were 59.4 ± 11.7 and 62.4 ± 13.4 at baseline and increased over the study period by 11.1 ± 18.6 (20.9% ± 35.2)

Table 8.1. Baseline characteristics for ESWT (n=31) and placebo control (n=31) groups

ESWT-group N=31

Placebo-group N=31

Total group N=62

Personal characteristicsAge (yr) 24.2 ± 5.2 25.7 ± 4.5 24.9 ± 4.9

Sex (men/women) 20/11 21/10 41/21

Height (m) 181.6 ± 10.0 181.6 ± 9.2 181.6 ± 9.5

Mass (kg) 80.1 ± 15.6 78.3 ± 13.1 79.2 ± 14.3

Training hours (h/wk) 3.4 ± 1.8 2.9 ± 1.4 3.1 ± 1.6

Clinical characteristicsVISA-P at baseline 59.4 ± 11.7 62.4 ± 13.4 60.9 ± 12.6

Duration of symptoms (months)

7.3 ± 3.6 8.1 ± 3.8 7.7 ± 3.7

Unilateral/bilateral symptoms

18/13 13/18 31/31

Location of pain: proximal/midtendon/distal (only for treated tendons)

29/1/1 27/2/2 56/3/3

100 Chapter 8

and 10.4 ± 15.5 (18.8% ± 30.6), respectively (Figure 8.2). There was a significant effect for time (p<0.01) but no treatment x time interaction effect (p=0.82). Secondary outcome measuresVAS for pain during ADL, sports, during 1 and 10 single-leg decline squats, after 3 maxi-mum single leg jumps and after the triple-hop test decreased during the follow-up pe-riod, but no significant differences were found between the ESWT and the placebo group. (Table 8.2)One week after treatment significantly more athletes in the treatment group than in the placebo group reported that their symptoms had improved and evaluated the treatment as beneficial (65% vs. 32%, χ2=6.46 p=0.01). One week after treatment more athletes from the ESWT group answered that they would recommend their treatment for this injury to family and friends (84% vs. 52%, χ2=7.38 p=0.01).

Figure 8.2. VISA-P score. Self reported VISA-P scores for the ESWT and placebo control groups before and 1, 12 and 22 weeks after (placebo) treatment

Placebo

ESWT

100

90

80

70

60

50

40

30

20

10

0

VIS

A-P

sco

re

Time

inclusion 1 week 12 weeks 22 weeks


8

Tabl

e 8.

2. M

ain

outc

ome

mea

sure

s at

1, 12

and

22

wee

ks in

the

ESW

T an

d Pl

aceb

o gr

oup

ESW

T (n

= 3

1)Pl

aceb

o (n

= 3

1)

Bas

elin

em

ean

(SD

)

1 wee

km

ean

(SD

)

12

wee

ksm

ean

(SD

)

22

wee

ksm

ean

(SD

)

Bas

elin

em

ean

(SD

)

1 wee

km

ean

(SD

)

12

wee

ksm

ean

(SD

)

22

wee

ksm

ean

(SD

)

Dif

fere

nce

(95%

CI)

at

1 wee

k #

Dif

fere

nce

(95%

CI)

at

12 w

eeks

#

Dif

fere

nce

(95%

C

I) a

t 22

wee

ks #

VIS

A s

core

(0

-100

)59

.4

(11.7

)66

.8

(16.

2)66

.7

(17.

5)70

.5

(18.

9)62

.4 (1

3.4)

66.3

(1

9.0)

68.9

(2

0.3)

72.7

(1

8.0)

3.6

(-3.

2 to

10

.4)

0.8

(-7.

7 to

9.3

)0.

7 (-

8.0

to

9.4)

Pain

dur

ing

AD

L

(0-1

0)2.

9

(1.8

)2.

1 (2

.0)

2.2

(2.2

)2.

1 (2

.5)

3.4

(2.0

)2.

7 (2

.2)

2.9

(2.5

)2.

3 (1

.9)

-0.2

(-

1.2 to

0.8

)-0

.3

(-1.4

to 0

.9)

0.2

(-1.0

to 1.

4)

Pain

dur

ing

spor

ts

(0-1

0)4.

9(2

.3)

3.8

(2.4

)4.

4 (2

.6)

3.2

(2.7

)4.

6 (2

.3)

3.8

(2.8

)4.

2 (3

.1)4.

0 (3

.0)

-0.4

(-1.8

to

1.0)

-0.2

(-

1.6 to

1.3)

-1.0

(-

2.6

to 0

.6)

Pain

dur

ing

1 dec

line

squa

t on

inju

red

leg

(0-1

0)3.

5(2

.8)

2.6

(2.8

)2.

5 (2

.7)

2.4

(2.6

)3.

5 (3

.1)3.

0 (2

.8)

2.7

(2.7

)2.

6 (2

.5)

-0.4

(-

1.8 to

1.0)

-0.1

(-1.7

to 1.

4)-0

.2

(1.6

to 1.

2)

Pain

dur

ing

10 d

eclin

e sq

uats

on

inju

red

leg

(0

-10)

4.6

(2

.8)

3.6

(2.6

)3.

3(2

.6)

3.2

(2.9

)4.

6 (2

.9)

4.1

(2.9

)3.

8 (3

.1)3.

6 (3

.0)

-0.5

(-

1.7 to

0.7

)-0

.5

(-1.8

to 0

.9)

-0.4

(-

1.6 to

0.8

)

Pain

dur

ing

3 si

ngle

-leg

ju

mps

on

inju

red

leg

(0

-10)

3.9

(2

.6)

2.7

(2.2

)2.

8 (2

.3)

3.0

(2.9

)4.

4 (2

.6)

3.6

(2.8

)3.

3 (2

.8)

2.9

(2.7

)-0

.4

(-1.4

to 0

.6)

-0.2

(-

1.2 to

0.9

)0.

5 (-

0.7

to 1.

7)

Pain

dur

ing

trip

le ju

mp

on in

jure

d le

g

(0-1

0)

4.4

(2

.5)

3.3

(2.5

)2.

9 (2

.0)

3.1

(2.8

)4.

3 (2

.6)

3.5

(2.6

)3.

3 (2

.9)

2.7

(2.3

)-0

.3 (-

1.3 to

0.7

)-0

.5

(-1.6

to 0

.7)

0.3

(-0.

9 to

1.6)

102 Chapter 8

Concurrent sports participation, treatment and pain medication There were no differences with regard to sports participation (number of training hours) and concurrent medical treatment between the ESWT and the placebo group during the follow-up period. There was no significant difference in the use of pain or anti-inflamma-tory medication between both groups.

Success of blindingBoth the outcome assessors and the athletes were blinded during the entire trial. Blinding appeared to be successful, since after the last evaluation 18 of the 30 (60%) athletes in the ESWT group guessed correctly that they had received real ESWT treatment, and 17 out of 27 (56%) athletes in the placebo group guessed correctly that they received placebo treatment.

Discussion

The main finding of this randomised placebo controlled study was that our patient-guided ESWT treatment procedure during the competitive season provided no benefit over pla-cebo treatment in the management of actively competing jumping athletes with patellar tendinopathy with symptoms for less than 12 months. VISA-P scores reflecting symptoms, knee function and sports participation improved significantly in both the ESWT and the placebo group over the 22-week study period, yet no significant differences between the groups were found.This is the first randomised controlled trial to evaluate the effectiveness of ESWT in a ho-mogenous group of actively playing athletes with rather mild patellar tendon pain lasting 3 to 12 months. Unfortunately the number of 68 subjects calculated a priori was not achieved. Since inclusion, treatment and final evaluation had to be scheduled within one competitive season to rule out any effects of rest and recovery in the off-season period, the inclusion pe-riod was very limited. However, the homogenous group of 62 included athletes had a lower VISA-P standard deviation than expected a priori. A post-hoc power analysis shows that with this actual lower standard deviation the included number of participants should have been sufficient to detect the postulated difference.There are some potential explanations for the absence of a beneficial ESWT effect in the TOPGAME study. This study was performed in athletes with rather mild symptoms last-ing less than 12 months, while previous randomised clinical studies that found positive results of ESWT included mainly athletes with chronic severe patellar tendinopathy who were treated in a hospital-based setting after several conservative treatments had already failed.21,22 One can presume that the athletes in our study with a mean VISA score of 60 and mean duration of symptoms of 8 months were suffering from reactive tendinopathy or early tendon disrepair in the continuum of tendon pathology, as described by Cook.23 The baseline ultrasound images obtained from some of the subjects confirm this presumption. Patients in previous RCTs had much lower VISA-P scores (around 45 points) and a longer and more variable duration of symptoms (>14 months),21,22 therefore it is likely that their


8

patellar tendons were in a more degenerative stage of tendon disease. It seems thus possible that ESWT is not an effective treatment modality for mild patellar tendinopathy in the early stages of the disease. Another explanation might be that athletes continued participating in their usual training and matches during the treatment and follow-up period and received no restrictions with regard to sports participation during the season. Bosch et al. (2009) demonstrated in ponies that even exposure of normal tendinous tissue to electrohydrauli-cally generated shockwaves of 0.14 mJ/mm2 leads to disorganization of the collagen net-work for up to six weeks.24 They advised restricting exercise in recently treated patients. It is possible that in our study the total load on the tendon due to the combination of both ESWT-induced collagen disorganization and the mechanical overload from training and matches was too high and there was insufficient time for recovery. This might have inter-fered with potential reparative effects of ESWT. A similar phenomenon was found in a study by Visnes et al. (2005), who could not detect an effect from a 12-week eccentric training program in a group of volleyball players with jumper’s knee who still trained and competed during the intervention period.25 Different results might have been found if athletes had been removed from training and matches, or if the intervention and follow-up period had been out of season. For example, Wang et al. (2007) found excellent results when athletes with chronic patellar tendinopathy were not allowed to perform heavy activities, including sports, 4-6 weeks after their ESWT treatment;22 however, improvement in their study might have been caused by this long period of rest in combination with ESWT treatment. Other possible explanations for not finding a positive effect of ESWT could be the chosen ESWT protocol and treatment approach. To our knowledge there is no consensus on the most appropriate and effective ESWT treatment protocol.11 We decided to treat the athletes with piezoelectric-generated focused shockwaves, in three sessions of 2000 impulses at a weekly interval using a patient-guided approach to determine the increase of energy den-sity and localization of treatment. This protocol was based on our previous experience and was tested in a pilot study.17 The total amount of energy and mean and maximum energy density in this study were higher than in previous studies on this topic.11 Although no local anaesthesia was used, it was well tolerated by the athletes and no side effects were reported, the energy density might have been too high. In animal studies it was demonstrated that electromagnetically- or electrohydraullically-generated shockwaves with energy densities above 0.5-0.6 mJ/mm2 can give rise to oedema within the paratenon and can result in histo-logical changes like fibroid necrosis, fibrosing of the paratenon and infiltration of inflam-matory cells.26,27 The fact that some of our athletes received treatment in this high-energy density range could have influenced our results; however, it remains uncertain if the afore-mentioned damage also occurs after treating the human patellar tendon with piezoelec-trically generated shockwaves. VISA-P scores improved during the follow-up period, so we believe that our treatment approach had no detrimental effects on the patellar tendons. We cannot rule out that the rather high energy density levels resulted in less beneficial ef-fects than expected though. A limitation with regard to the treatment protocol was that the placebo group might have received a very minimal dose of ESWT. The energy density in studies that found ESWT to be effective were much higher than this minimal dose, so it is not plausible that this caused the improvement in our placebo group. On the other hand, it

104 Chapter 8

might also be possible that especially very minimal doses of ESWT are effective in athletes with mild patellar tendinopathy of rather short duration when tendon degeneration has not occurred yet.Furthermore, since we were interested in the effectiveness of ESWT alone we did not add other exercises or treatments to our intervention protocol, making sure a potential effect was caused by ESWT and not by other co-interventions. However, it is known that athletes with patellar tendinopathy can benefit from a more comprehensive rehabilitation program including pain management, reduction of load, and an exercise program to improve muscle tendon-function and to normalize the kinetic chain.28 Peers et al. (2003) demonstrated that a combination of ESWT and eccentric training was effective in patients with chronic patel-lar tendinopathy.21 This could also explain the difference between our results and positive results of ESWT in other studies.Despite the fact that we have to conclude that ESWT appeared not to be effective in the TOPGAME study, considering the aforementioned explanations we still believe ESWT might be useful in the rehabilitation of athletes with patellar tendinopathy. Additionally, al-though in our study no significant differences between the groups were found for the VISA-P and VAS pain scores during the entire study period, most improvement in the ESWT group was recorded during the first week post-treatment. It was also remarkable that one week after the end of the treatment significantly more athletes from the ESWT group reported that their symptoms had improved and that they would recommend ESWT to family and friends as treatment for patellar tendinopathy. Previous animal studies demonstrated poten-tial explanations for short-term (and long-term) pain relief. Hyperstimulation analgesia, de-struction of unmyelinated nerve fibres and suppression of neurotransmitters Substance-P and Calcitonin Gene-related peptide have been described as underlying mechanisms for this antinociceptive effect of ESWT.29-33 ESWT thus seems to produce some short-term improve-ment of symptoms in this group of athletes with mild patellar tendinopathy lasting than 12 months. It can be hypothesized that symptoms further improved when athletes stopped playing and did additional exercises as part of a combined rehabilitation program.

Conclusions

The TOPGAME study demonstrates that ESWT as monotreatment during the competi-tive season has no benefit over placebo treatment in the management of actively compet-ing jumping athletes with patellar tendinopathy with mild symptoms lasting than 12 months. It is possible that ESWT does not influence tendinopathy in this early stage of the disease, that the combined load of ESWT and continuation of training is too high and interferes with tendon regeneration, or that our treatment protocol needs to be adjusted. These findings do not conclusively mean that the use of ESWT in patellar tendinopa-thy should be ceased. Since athletes reported subjective improvement after one week, no detrimental effects were elicited and there is growing evidence for the effectiveness of treatment programs for tendinopathies combining ESWT and eccentric training.21,34 Fur-ther trials evaluating the most appropriate treatment strategy for each stage of patellar tendinopathy seem warranted.


8

Acknowledgements This study was funded by the Netherlands Organisation for Health Research and Development (Zon-

MW), grant number 750.20.010. We would like to thank Gerard Koel, Robert van Oosterom, Joris van

der Togt, Nynke Visser, Hans de Vries, Lydia Willemse and the TOPGAME students for their help with

the TOPGAME study. We extend special thanks to Alex Essers, Toine Leinse, Patrick Martens, Yvonne

Stevens and Tetske van der Weg, physical therapists at TopSupport Sports Medicine Centre Eindhoven

and at the University Hospitals of Maastricht and Groningen, who provided the ESWT treatment.

Finally, we thank the Dutch Basketball, Volleyball and Handball associations for their logistic support

toward contacting the athletes.

106 Chapter 8


North Am; 4:665-78.


3. Zwerver J, Bredeweg SW. Prevalence of jumper’s knee among non-elite athletes from three different sports. Abstract book of the XXIX FIMS World Congress of Sports Medicine,Beijing, 2006 , 273. 2006.








11. van Leeuwen MT, Zwerver J, Akker-Scheek I (2009). Extracorporeal shockwave therapy for patellar tendinopathy: a review of the literature. Br J Sports Med; 43:163-8.

12. Zwerver J, Verhagen E, Hartgens F, Akker-Scheek I, Diercks RL (2010). The TOPGAME-study: effectiveness of extracorporeal shockwave therapy in jumping athletes with patellar tendinopathy. Design of a randomised controlled trial. BMC Musculoskelet Disord; 11:28.



15. Shalaby M, Almekinders LC (1999). Patellar tendinitis: the significance of magnetic resonance imaging findings. Am J Sports Med; 27:345-9.

16. Rompe JD, Meurer A, Nafe B, Hofmann A, Gerdesmeyer L (2005). Repetitive low-energy shock wave application without local anesthesia is more efficient than repetitive low-energy shock wave application with local anesthesia in the treatment of chronic plantar fasciitis. J Orthop Res; 23:931-41.

17. Zwerver J, Dekker F, Pepping G. Patient Guided Piezo-electric Extracorporeal Shockwave Therapy as Treatment for Chronic Severe Patellar Tendinopathy; a pilot study . Journal of Back and Musculoskeletal Rehabilitation. In press 2010.


8




21. Peers KH (2003). Extracorporeal Shock wave therapy in chronic Achilles and Patellar tendinopathy Catholic University Leuven, Belgium.


23. Cook JL, Purdam CR (2009). Is tendon pathology a continuum? A pathology model to explain the clinical presentation of load-induced tendinopathy. Br J Sports Med; 43:409-16.

24. Bosch G, de Mos M, van Binsbergen R, van Schie HT, van de Lest CH, van Weeren PR (2009). The effect of focused extracorporeal shock wave therapy on collagen matrix and gene expression in normal tendons and ligaments. Equine Vet J; 41:335-41.

25. Visnes H, Hoksrud A, Cook J, Bahr R (2005). No effect of eccentric training on jumper’s knee in volleyball players during the competitive season: a randomized clinical trial. Clin J Sport Med; 15:227-34.

26. Maier M, Tischer T, Milz S, Weiler C, Nerlich A, Pellengahr C, Schmitz C, Refior HJ (2002). Dose-related effects of extracorporeal shock waves on rabbit quadriceps tendon integrity. Arch Orthop Trauma Surg; 122:436-41.

27. Rompe JD, Kirkpatrick CJ, Kullmer K, Schwitalle M, Krischek O (1998). Dose-related effects of shock waves on rabbit tendo Achillis. A sonographic and histological study. J Bone Joint Surg Br; 80:546-52.


29. Hausdorf J, Lemmens MA, Heck KD, Grolms N, Korr H, Kertschanska S, Steinbusch HW, Schmitz C, Maier M (2008). Selective loss of unmyelinated nerve fibers after extracorporeal shockwave application to the musculoskeletal system. Neuroscience; 155:138-44.

30. Hausdorf J, Lemmens MA, Kaplan S, Marangoz C, Milz S, Odaci E, Korr H, Schmitz C, Maier M (2008). Extracorporeal shockwave application to the distal femur of rabbits diminishes the number of neurons immunoreactive for substance P in dorsal root ganglia L5. Brain Res; 1207:96-101.


32. Ogden JA, Alvarez RG, Levitt R, Marlow M (2001). Shock wave therapy (Orthotripsy) in musculoskeletal disorders. Clin Orthop Relat Res;22-40.

33. Ohtori S, Inoue G, Mannoji C, Saisu T, Takahashi K, Mitsuhashi S, Wada Y, Takahashi K, Yamagata M, Moriya H (2001). Shock wave application to rat skin induces degeneration and reinnervation of sensory nerve fibres. Neurosci Lett; 315:57-60.

34. Rompe JD, Furia J, Maffulli N (2009). Eccentric loading versus eccentric loading plus shock-wave treatment for midportion achilles tendinopathy: a randomized controlled trial. Am J Sports Med; 37:463-70.

Chapter 9

General discussion

General discussion 111

9

Introduction

Patellar tendinopathy still remains a difficult-to-treat overuse injury of the patellar ten-don with a very negative impact on the careers of many athletes (Chapter 2), therefore prevention programs and interventions aimed at a fast return to play are important. These can only be developed if the extent and severity of the problem and its aetiology and injury mechanism are known. This thesis focused on patellar tendinopathy in non-elite athletes and the evaluation of the effectiveness of ESWT in managing this condition. Prevalence of patellar tendinopa-thy (Chapter 3) appears to be high among non-elite athletes as well (2.5-14.4%). Male ath-letes are affected twice as much as female athletes. Sport-specific loading characteristics, age, height and weight seem to be risk factors associated with patellar tendinopathy.In order to evaluate the outcome of different treatment interventions, feasible cross-cul-tural and validated outcome measures and specific functional test for patellar tendinopa-thy are necessary. The translated Dutch version of the VISA-P questionnaire turned out to be equivalent to its original version, has satisfactory test-retest reliability, and is a valid score to evaluate symptoms, knee function and ability to perform in sports of Dutch athletes with patellar tendinopathy (Chapter 4). Biomechanical analysis of the single-leg decline squat revealed that this exercise can increase patellar tendon force and therefore seems suitable for use as a functional loading test for the patellar tendon in athletes with patellar tendinopathy (Chapter 5).From what is known in the literature so far, ESWT seems to be a safe and promising treatment for chronic patellar tendinopathy with a positive effect on pain and function. However, based on current knowledge it is impossible to recommend a specific treat-ment protocol (Chapter 6). No studies into the effectiveness of ESWT in athletes with patellar tendinopathy for less than 12 months who are still actively competing have been conducted before. We therefore designed the TOPGAME study, the first randomised con-trolled trial into the effectiveness of ESWT on pain, symptoms and function of athletes with early symptomatic patellar tendinopathy who are still in training and competition (Chapter 7). Based on this multicentre study we concluded that ESWT as monotreatment during the competitive season has no benefit over placebo treatment in the management of actively competing jumping athletes with patellar tendinopathy who have symptoms for less than 12 months (Chapter 8).

In this general discussion the results of the research described in the previous chapters are examined in a broader perspective. The first part of this chapter describes the epi-demiology of patellar tendinopathy in athletes and its implications for prevention. The second part focuses on the different assessment tools that might be used as outcome mea-sures for patellar tendinopathy. In the third part the role of ESWT, amongst other treat-ment options, in the management of patellar tendinopathy is discussed. If applicable, clinical implications and further research suggestions are presented.

112 Chapter 9

Epidemiology and prevention of patellar tendinopathyThe first step in the sequence of sports injury prevention research (Figure 9.1), as out-lined by Van Mechelen et al. in 1992,1 is to describe the magnitude of the problem in terms of the frequency and severity of injuries. Overuse injuries might represent as much of a problem as do acute injuries in many sports. However, the frequency and severity of overuse injuries is often underestimated because only the incidence of these injuries is reported and a ‘time-loss injury’ defini-tion is being used. Many athletes continue their sporting activities despite their chronic overuse injury. This means that in many epidemiological studies, despite their prevalence overuse injuries are not included in the incidence rate as new injuries that cause time loss from sports. When this ‘traditional’ study approach is used for the overuse injury of pa-tellar tendinopathy, an underestimation of the problem can be expected.2 For this reason, Bahr made the following recommendations on how overuse injuries can be quantified in a more appropriate standardised method. (a) studies should be prospective, with continuous or serial measurements of symp-

toms; (b) valid and sensitive scoring instruments need to be developed to measure pain and

other relevant symptoms; (c) prevalence and not incidence should be used to report injury risk; (d) severity should be measured based on functional level and not time loss from

sports.

Although the study described in Chapter 3 was not prospective, it did show that patellar tendinopathy is a common and often chronic problem not only in elite but also in non-elite athletes. In non-elite jumping sports the prevalence was over 10% and mean duration of

1. Establishing the magnitude of the injury problem in terms of frequency and severity

2. Establishing etiology andmechanism of injury

3. Developing and introducing apreventive measure

4. Assessing its effectiveness byrepeating step 1 or by conducting a(randomised) controlled trial

Figure 9.1. The sequence of prevention of sports injuries. Modified from: Van Mechelen 19921


9symptoms was more than one and a half years. The Dutch VISA-P score was used as scoring instrument; it has been demonstrated to be valid and sensitive to measure pain, other symptoms and functional level of sports in these athletes. The non-elite athletes in the study still continued to play despite their symptoms, but the mean VISA-P score of 71 (out of 100) points to their inability to compete at their full potential. This thesis has thus shown that patellar tendinopathy is common and impeding among non-elite athletes too, therefore preventive strategies seem warranted for this treatment-challenged injury.The next step in the sequence of prevention of sports injuries is to map out the causes of injuries in order to identify their risk factors and mechanisms. Since overuse injuries, including tendinopathies, seem to have a multifactorial aetiology, this is not an easy step. Both intrinsic and extrinsic factors have been described in the literature (Table 9.1),3 but there is little robust and often even conflicting evidence for these factors.4 Among all potential risk factors, the loading characteristics of the sport – especially landing – are increasingly considered important factors in the aetiology of patellar ten-dinopathy. Bisseling et al. demonstrated that athletes with a ‘stiffer’ landing pattern are more at risk for developing jumper’s knee.5,6 More recently, Edwards showed that asymp-tomatic athletes with and without a patellar tendon abnormality (PTA) had different land-ing strategies.7 Athletes with PTA landed with significantly greater knee flexion and extended their hips while the controls flexed their hips as they landed. These findings provide both trainers and clinicians with important landing assessment criteria against which to identify athletes at risk of developing patellar tendinopathy. Moreover, landing strategy is a factor that can be modified and might therefore be important towards pre-venting patellar tendinopathy in jumping athletes. Although in the last decades some progress has been made in elucidating the underlying pathological process of (patellar) tendinopathy, little is known about the link between mechanical loading and the pathophysiological response in the tendon. Clarification of

Table 9.1. Predisposing factors for patellar tendinopathy (modified from Brukner & Khan, Clinical Sports Medicine, 3rd ed., 2006 McGraw-Hill, Australia).

Intrinsic factors Extrinsic factors

Gender Training (volume, intensity, type, increase)

Genetic factors Technique (jumping, landing)

Age Playing surface (hard, soft)

Size and body composition Shoes and equipment

Malalignment Environmental conditions

Leg length discrepancy Psychological conditions

Muscle imbalance and weakness Nutrition

Lack of flexibility /restricted range of motion Medication

114 Chapter 9

this complex underlying working mechanism together with other prospective studies in-vestigating the various risk factors and their influence on the tendon would certainly aid in establishing more appropriate and effective preventive measures. A lot of research has to be done before these intriguing and important questions can be answered.Steps 3 and 4 of the sequence of injury prevention need to be investigated in future stud-ies. Developing and introducing a training program that teaches athletes how to land in the most appropriate way could be one important preventive measure to reduce the risk of developing patellar tendinopathy. One should realise though that only programs that can and will be adopted by athletes, coaches and sporting associations will be successful in preventing injuries.8 Hence implementation strategies and effect research are also nec-essary to evaluate if preventive methods really are being adopted by the athletes. Finally, the costs and effectiveness of the introduced preventive measures should be evaluated by repeating step 1, or preferably by conducting a randomised controlled trial.

Diagnostic and outcome assessment tools

Next to the fact that the pathophysiological mechanism of patellar tendinopathy has not been elucidated, research and clinical management are also hampered by a lack of firm diagnostic tools and criteria as well as a limited number of reliable evaluation tools. Novel tools are needed to diagnose patellar tendinopathy, monitor progress during a rehabilita-tion program and evaluate the effectiveness of interventions. So far, clinical examination still represents the gold standard in the diagnosis of patellar tendinopathy. It is based primarily on a history of activity-related anterior knee pain as-sociated with well-localised, palpable patellar tendon tenderness.9-11 This means that dif-ferentiating between patellar tendinopathy and other pathologic entities causing anterior knee pain can sometimes be difficult.Pain on palpation thus plays an important role in the diagnosis and follow-up evaluations of patellar tendinopathy. Palpation pressure and the evoked pain can also be measured in a standardised way using an algometer.12 Determining the pressure pain threshold with an algometer seems to be a feasible and reliable method that might be useful to objectify the longitudinal effects of interventions in patients suffering from patellar tendinopa-thy.13

Another frequently used assessment tool is the VISA-P questionnaire, which was specifi-cally designed for rating the severity of patellar tendinopathy.14 This brief questionnaire is not a diagnostic tool but assesses symptoms, simple tests of function and the ability to undertake physical activity. It therefore fits into the aforementioned recommendations of Bahr. In Chapter 4 a Dutch version of this questionnaire was developed and validated, so this evaluation tool is now also available for research among Dutch-speaking athletes. Deployment of this easy-to-use, reliable and valid scoring instrument is therefore rec-ommended in future studies on patellar tendinopathy. Since this questionnaire has also been translated into other languages, comparison of studies from different countries is possible.15,16

Next to a questionnaire that determines patient-based outcome, functional tests are con-


9

sidered useful. The single-leg decline squat as an additional evaluation tool is therefore recommended for use in patients with patellar tendinopathy. This simple function test can increase patellar tendon load up to 40%. Purdam et al. also recommend this test because it has the best discriminative ability in the physical assessment of patellar tendinopathy and can be easily performed in a standardised way.17 The research described in this thesis also uses the maximal vertical jump test and triple hop test as evaluation tools. These evaluation tools combine specific tests of function, pain scores and objective performance outcomes (jumping height or distance); they are easily performed functional tests that give a good impression of how painful loading of the patellar tendon is, and appear suit-able for monitoring athletes with patellar tendinopathy. However, validation studies and research into the link between these functional tests and, for example, the VISA-P score and imaging abnormalities are necessary and should be object of future studies.

The role of imaging in diagnosis and outcome assessmentThe usefulness of imaging techniques in the diagnosis and follow-up of patellar tendi-nopathy remains controversial. Magnetic resonance imaging (MRI) and grey-scale ultra-sonography (GS-US) are often used in the diagnostic work-up, and both provide excel-lent anatomic representation of the patellar tendon.10,11,18 In recent years Colour-Doppler (CD-US) and Power-Doppler Ultrasound (PD-US) have also been used to show neovas-cularisation in tendinopathies.19,20 Nerves accompanying these vessels might play a role in the pain observed in tendinopathies.21-23 Histopathological studies have demonstrated the characteristic tendinopathy appearances observed with both MRI and GS-US to be caused by the underlying pathological tendon changes.24-26 Warden et al. studied the com-parative accuracy of US and MRI, and concluded that US was more accurate than MRI in confirming clinically diagnosed patellar tendinopathy. GS-US and CD-US may represent the best combination for confirming clinically diagnosed patellar tendinopathy because GS-US had the greatest sensitivity, while a positive CD-US test result indicates a strong likelihood of an individual being symptomatic.27

One should realise however that it is not uncommon for symptomatic tendons to have the MRI or GS-US appearance of normal asymptomatic tendons; imaging abnormali-ties characteristic of patellar tendinopathy can be found in asymptomatic tendons.19,24,28-34 The role of MRI and US in the follow-up and evaluation of treatment of athletes with patellar tendinopathy is also debated. A number of studies has shown that both before and after a treatment intervention the correlation between clinical findings and US and MRI imaging is low.29,35,36 It has also been demonstrated that symptoms, tendon changes on GS-US and MRI and degree of neovascularisation on CD-US can vary independently, even during the course of a season.29,31,32,37-39 Recently Malliaras et al. suggested that these transitions in GS-US may represent different phases of tendon pathology.40 This interest-ing concept which certainly merits further investigation is discussed in more detail in the next section. Another promising development is ultrasonographic tissue characterisation (UTC),41-44 a novel non-invasive technique that visualises the structure of tendon tissue and quantifies its structural integrity with an excellent reproducibility. Different stages of pathology and regeneration within the tendon are visualised in a standardised and operator-independent way. As such, UTC might be a very useful quantitative method to monitor and evaluate treatment protocols of athletes with a tendinopathy. Future studies

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should address the value of US-GS, US-CD, MRI and UTC in the diagnosis, staging and follow-up of athletes with patellar tendinopathy.

Management of patellar tendinopathy

Although some progress has been made in recent decades, the clinical management of patellar tendinopathy remains problematic. Athletes of different ages with tendons ex-posed to various loads present acute or chronic symptoms and varying degrees of pain and functional limitation. Numerous management options have been tried, including rest, (eccentric) exercise, training modification, splinting, taping, cryotherapy, electrotherapy, pharmaceutical agents such as nonsteroidal anti-inflammatory drugs (NSAIDs), various (peri)tendinous injections and different surgical procedures.10,11,45-47 However, the success rate of these interventions is quite divergent. Another management option, ESWT, was under study in this thesis (Chapters 6, 7 and 8). Based on a review it was concluded that, notwithstanding the limited evidence, ESWT seems to be a safe and promising treatment for athletes with patellar tendinopathy. How-ever, no significant treatment effect was found in the TOPGAME study, in which patient-guided focused piezoelectric ESWT was compared to sham ESWT treatment in actively playing athletes with symptoms for less than 12 months. It has to be concluded that ESWT is not the optimal treatment option either. Some patients did benefit from the ESWT treatment though. Further analyses should determine whether predicting factors can be found.Overall it has to be concluded that the search for the optimal treatment strategy for patel-lar tendinopathy has not yet ended; why some tendons recover with simple interventions while others remain resistant to all kinds of treatments remains to be answered. This is frustrating for the athlete as well as the treating physician. Moreover, it is unclear why a certain treatment is successful for one athlete and has no effect on another. A potential explanation might be found in the ‘continuum of tendon pathology’ model.48

Continuum of tendon pathologyThe underlying pathology of tendinopathy has previously been described as degenera-tive or failed healing. However, this rather simplified description of a complex pathophys-iological process does not fully explain the heterogeneity in presentation and variability in recovery. Cook and Purdam recently proposed a new model of tendinopathy, based on available evidence from pathological, clinical and imaging studies.48 This ‘continuum of tendon pathology’ (Figure 9.2) describes three distinct stages: (1) reactive tendinopathy, (2) tendon dysrepair (failed healing) and (3) degenerative tendinopathy. Clinical and imaging features allow a tendon to be classified as one of these stages (Table 2). One should however keep in mind that there is continuity between these stages and that combined stages can exist within a tendon. As mentioned before the role of ultra-sound imaging remains equivocal. This hypothetical yet interesting model requires fur-ther scientific and clinical evaluation.


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Table 9.2. Clinical and imaging features of different stages of tendon pathology48

Clinical manifestation Ultrasound Imaging

Reactive tendinopathy Acute overload in athlete Fusiform swollen tendon, collagen fascicles intact with hypoechogenic zones in-between

Tendon dysrepair Chronic overload in young athlete

Discontinuity of collagen fascicle and small focal areas of hypoechogenicity, vascularisation

Degenerative tendinopathy Chronic overload in older or elite athlete

Extensive hypoechogenicity and vascularisation, few reflections from collagen fascicles

Figure 9.2. Pathology continuum; this model embraces the transition from normal through to degenerative tendinopathy and highlights the potential for reversibility early in the continuum.

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Table 9.3. Clinical and pharmacological treatments placed in the model48

Stage Pharmacological management Physical management

Reactive tendinopathy/early tendon dysrepair

Tenocyte inhibitors (ibuprofen, celecoxib, corticosteroids), aggrecan inhibitors (ibuprofen, naproxen sodium, indomethacin)

Load management. Reduction in frequency ± intensity of tendon load

Late tendon dysrepair/degeneration

Prolotherapy, blood, platelets, platelet-rich plasma, aprotinin, sclerosing therapy, glyceryl trinitrate

Exercise with eccentric component, ESWT, frictions, ultrasound

This conceptual model might also facilitate the rational placement of treatments along the continuum. Common interventions and their proposed place in the ‘continuum model’ are summarised in Table 3. It must be stipulated that this is only a simplified and hypo-thetical framework, designed for further investigation and clinical evaluation.Currently there tends to be no difference in the treatment approach between for example a young active athlete with a (sub)acute tendon problem and a more sedentary older per-son with a chronic tendinopathy. If both started an intensive eccentric exercise program, different outcomes can be expected. This might also explain the variable and sometimes conflicting results from intervention studies in (patellar) tendinopathies. If the included study population differed in its stage of tendon pathology, some athletes received the appropriate treatment while others received a ‘wrong’ treatment which is inappropriate for their underlying stage of pathology. This would have had a negative influence on the outcome of the studies. The situation gets even more complicated if one realises that it is highly probable that some tendons have discrete regions that are in different stages at one time.49 For example, tendons with degenerative changes can acutely be overloaded, lead-ing to heterogeneous pathology in a single tendon. Treatment of these complex tendon situations requires an even more differentiated approach.For these reasons, both researchers and clinicians should be aware of this continuum of tendon pathology (as well as the limitations of this simplified concept) when designing a study or treating an athlete with patellar tendinopathy. In the early stages, reduction of load is important to reduce pain and to give the tendon time to recover. The frequently used daily eccentric exercise program is less appropriate in this phase of the disease and can even aggravate symptoms. Although it has been reported that NSAIDs and corticos-teroids have a negative effect on tendon repair in the long term,50 they might be useful in reactive tendinopathy, as they reduce the pain and inhibit the tenocytes from producing excess ground substance proteins responsible for the swelling of the tendon.51,52 In reac-tive tendinopathy, NSAIDs and corticosteroids ‘calm down’ the tendon.


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Treatments that stimulate collagen synthesis and restructuring of the matrix need to be used in the late dysrepair and degenerative stages. Exercise – particularly slightly painful eccentric exercises – appear to be a positive stimulus for these processes.52-54 Further, ec-centric exercise has been demonstrated to be beneficial for pain relief as well as return to function and activity.55 Frictions and ultrasound can also increase production of collagen but are less effective than exercise.56 Extracorporeal shockwave therapy might also give pain relief.57-60 In animal studies it was demonstrated that it can increase collagen synthe-sis and improve the structure of the tendon.59,61

Several other treatments that are considered to influence the healing and remodelling process of the tendon have been proposed, among them injection treatments.47 An injec-tion itself (prolotherapy) can already have a beneficial effect on tendon structure.62 Blood or platelet-rich plasma injections (PRP) can stimulate cell proliferation and the healing process in the tendon.62-64 Injections with aprotinin, a collagenase inhibitor, are supposed to diminish collagen breakdown in the remodelling matrix.65 Ultrasound-guided sclerosis of neovessels appears to be effective in treating pain and improving tendon structure.66 Application of glyceryl trinitrate combined with eccentric training might also improve collagen synthesis.67 All seem to be promising treatments, but their role in the clinical management of patellar tendinopathy needs further investigation.

Treatment protocolNext to the need for more research to determine the optimal treatment at each stage of patellar tendinopathy, another problem is that for most treatment options there is no consensus about the most effective treatment protocols. For ESWT, for example, different shockwave devices are used. Electromagnetic, electrohydraulic and piezoelectric devices generate focused shockwaves, but there are differences between the shockwave character-istics of these devices. On the other hand, ballistic devices generate radial pressure waves with completely different characteristics, yet treatment provided with these devices is of-ten called radial shockwave therapy (RSWT) too. Positive results have been reported for both focused shockwave and radial pressure therapy, but it is difficult to compare these studies because of the different underlying technical principles. Not only the device used but also number of ESWT treatments, treatment interval, energy density and number of impulses can be varied; these are all important parameters that might influence the effectiveness of this treatment method.

Recommendations for future research in ESWT and patellar tendinopathyThe results of this thesis are not in line with previously published studies on the effective-ness of ESWT on patellar tendinopathy. This raises new questions on this topic that should be studied in future research. The following recommendations for future studies are made:

Research that elucidates pathophysiological mechanisms of patellar tendinopathy.•Clinical, imaging and pathology studies that further substantiate the continuum of •tendon pathology model.Studies on the working mechanism of ESWT and RSWT at different stages of tendi-•nopathy.Randomised controlled trials to investigate the effectiveness of ESWT and RSWT at •different stages of the disease.

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Randomised controlled trials to compare different devices and treatment protocols.•Studies that investigate the synergistic role of different treatment combinations, e.g. •eccentric training in combination with ESWT, platelet-rich plasma in combination with ESWT.

Conclusions

This thesis focussed on patellar tendinopathy among non-elite athletes and the evalu-ation of the effectiveness of ESWT in managing this condition. Based on the research described in this thesis it can be concluded that patellar tendinopathy is also a common overuse injury with a multifactorial aetiology among non-elite athletes. Developing and introducing preventive programs that change elements such as the landing strategy of jumping athletes seem warranted to reduce the risk of getting this difficult-to- treat knee injury. The Dutch VISA-P questionnaire is a valid and reliable tool to assess symptoms, func-tion and ability to play sports among Dutch athletes with patellar tendinopathy. The single-leg decline squat can be used as a functional test that specifically loads the patellar tendon. ESWT seems to be a promising treatment for patellar tendinopathy. However, no benefit of ESWT treatment was found in a multicentre randomised controlled trial (the TOPGAME study) investigating the effectiveness of ESWT in athletes with patellar tendinopathy with symptoms for less than 12 months. Further research is needed to determine the op-timal treatment strategy for patellar tendinopathy. Treatment options, including different ESWT protocols, should be placed in a rational manner along the continuum of tendon pathology. The effectiveness of interventions must be monitored using feasible, valid and sensitive scoring instruments.


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61. Bosch G, de Mos M, van Binsbergen R, van Schie HT, van de Lest CH, van Weeren PR (2009). The effect of focused extracorporeal shock wave therapy on collagen matrix and gene expression in normal tendons and ligaments. Equine Vet J; 41:335-41.

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63. Filardo G, Kon E, Della Villa S, Vincentelli F, Fornasari PM, Marcacci M (2010). Use of platelet-rich plasma for the treatment of refractory jumper’s knee. Int Orthop; 34:909-15.

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67. Paoloni JA, Appleyard RC, Nelson J, Murrell GA (2004). Topical glyceryl trinitrate treatment of chronic noninsertional achilles tendinopathy. A randomized, double-blind, placebo-controlled trial. J Bone Joint Surg Am; 86-A:916-22.

Chapter 10

Summary

Summary 129

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Patellar tendinopathy (formerly known as jumper’s knee) is a common and difficult-to-treat overuse injury of the patellar tendon with a very negative impact on the careers of many athletes. It appears to involve a failed healing process in the tendon, which has con-sequences for the treatment strategy. Rehabilitation programs are based on the principles of load reduction and an eccentric exercise program to improve muscle-tendon function and optimise the kinetic chain. Prolonged rehabilitation is necessary because of slow tendon recovery. Anti-inflammatory treatment is often unsuccessful. Surgery does not guarantee a quick symptom-free return to sport at the original level either. Extracorpo-real shockwave therapy, ultrasound-guided sclerosing of new vessels, and tendinous and peritendinous injections of aprotinin and autologous growth factors seem to be promis-ing new treatment options.The scope of this thesis is to increase our knowledge of patellar tendinopathy in non-elite athletes and the role of extracorporeal shockwave therapy (ESWT) in the management of this condition. The first objective is to describe the prevalence of patellar tendinopathy among non-elite athletes and to find associated risk factors for this overuse injury. The second objective is to develop and study specific (Dutch-language) evaluation tools for patellar tendinopathy. The third objective is to evaluate the effectiveness of ESWT as treatment for patellar tendinopathy.The aim of the research, described in Chapter 3, was to determine the prevalence of jumper’s knee among non-elite athletes from different sports as well as potential risk factors for this condition. To this end, 891 male and female non-elite athletes from seven popular sports in the Netherlands (basketball, volleyball, handball, korfball, soccer, field hockey and athletics) were interviewed. Using a specially developed questionnaire, in-formation was obtained about individual characteristics (age, height and weight), train-ing background, previous and current knee problems, and the VISA-P score. The overall prevalence of current jumper’s knee was 8.5% (78 of 891 athletes), with a significant dif-ference between sports with different loading characteristics and playing surfaces. Preva-lence was highest in volleyball players (14.4%) and lowest in soccer players (2.5%), and significantly higher in male athletes (51 out of 502, 10.2%) than in female athletes (25 out of 389, 6.4%). Mean duration of symptoms was 18.9 months (SD 21.6; range 2.0–59.8). The mean VISA-P score of the athletes with jumper’s knee was 71.4 (SD 13.8). Athletes with jumper’s knee were significantly older, taller and heavier than those without a jumper’s knee. From the results of this cross-sectional survey it was concluded that the prevalence of jumper’s knee is high among non-elite athletes and that jumper’s knee is almost twice as common among male non-elite athletes than female athletes. Different sport-specific loading characteristics of the knee extensor apparatus, playing surface, and age, height and weight seem to be risk factors associated with patellar tendinopathy. The VISA-P questionnaire evaluates severity of symptoms, knee function and ability to play sports of athletes with patellar tendinopathy. This English-language self-adminis-tered brief patient outcome score was developed in Australia to monitor rehabilitation and to evaluate outcome of clinical studies. Aim of Chapter 4 was to translate the ques-tionnaire into Dutch according to internationally recommended guidelines and to study the reliability and validity of the Dutch version of the VISA-P. Test-retest reliability was determined in 99 students with a time interval of 2.5 weeks. To determine discriminative validity of the Dutch VISA-P, 18 healthy students, 15 competitive volleyball players (at-

130 Chapter 10

risk population), 14 patients with patellar tendinopathy, 6 patients who had surgery for patellar tendinopathy, 17 patients with knee injuries other than patellar tendinopathy, and 9 patients with symptoms unrelated to their knees completed the Dutch VISA-P. The Dutch VISA-P questionnaire showed satisfactory test-retest reliability (ICC = 0.74). The mean (± SD) VISA-P scores were 95 (± 9) for the healthy students, 89 (± 11) for the volleyball players, 58 (± 19) for patients with patellar tendinopathy and 56 (± 21) for athletes who had surgery for patellar tendinopathy. Patients with other knee injuries or symptoms unrelated to the knee scored 62 (± 24) and 77 (± 24). This study demonstrated that the translated Dutch version of the VISA-P questionnaire is equivalent to its original version, has satisfactory test-retest reliability, and is a valid score to evaluate symptoms, knee function and ability to play sports of Dutch athletes with patellar tendinopathy.The single-leg squat on a 25° decline board has been described as a clinical assessment tool and as a rehabilitation exercise for patients with patellar tendinopathy. Several as-sumptions have been made about its working mechanism on patellar load and patell-ofemoral forces, but these are not substantiated by biomechanical evaluations. The aim of the study described in Chapter 5 was therefore to investigate knee moment and patel-lofemoral contact force as a function of decline angle in the single-leg squat. Five subjects performed single-leg eccentric squats at decline angles of 0°, 5°, 10°, 15°, 20° and 25° with/without a 10-kg backpack, and 30° on a board that was placed over a force plate. Kinematic and force plate data were recorded by the Optotrak system. Joint moments of ankle, knee and hip were calculated by two-dimensional inverse dynamics. Knee moment increased by 40% at decline angles of 15° and higher, whereas hip and ankle moment decreased. Maximum knee and ankle angles increased with steeper decline. With a 10-kg backpack at a 25° decline, the knee moment was 23% higher than unloaded. Both patel-lar tendon and patellofemoral forces increased with higher decline angles, but beyond 60° the patellofemoral force rose more steeply than the tendon force. It is concluded that all single-leg squats at decline angles >15° result in 40% increases in maximum patellar ten-don force. In knee flexions >60°, patellofemoral forces increase more than patellar tendon forces. Higher tendon load can be achieved by using a heavier backpack.The review in Chapter 6 summarises the current knowledge on extracorporeal shock-wave therapy (EWST) as a treatment for patellar tendinopathy. The purpose of this re-view was (1) to study the effectiveness of ESWT treatment for patellar tendinopathy, (2) to draft guidelines for an effective treatment protocol for ESWT treatment, and (3) to identify topics for further research. A computerised search of the Medline and Embase databases was conducted to identify studies dealing with the effectiveness of ESWT for patellar tendinopathy. Seven articles describing this effectiveness, all published after 2000, were included. These studies involved a total of 283 patients (298 tendons), 204 of whom (215 tendons) were assigned to ESWT treatment. The treatment results were posi-tive but most studies had methodological deficiencies, small numbers and/or short follow-up periods. Method of application and shockwave generation, energy level, number and frequency of treatments, use of (local) anaesthesia and method of localisation were vari-able. From this review it was concluded that ESWT seems to be a safe and promising treatment for patellar tendinopathy with a positive effect on pain and function. Based on current knowledge it is impossible to recommend a specific treatment protocol. Further basic and clinical research into the working mechanism and effectiveness of ESWT for

Summary 131

10

patellar tendinopathy are necessary.Chapter 7 presents the design of the TOPGAME study (Tendinopathy of Patella Gron-ingen Amsterdam Maastricht ESWT), which aims to determine the effectiveness of ESWT on athletes with patellar tendinopathy who were still in training and competition. The TOPGAME study is the first two-armed randomised controlled trial with blinded participants and outcome assessors that investigates the effectiveness of patient-guided focussed ESWT treatment (compared to placebo ESWT) on pain reduction and recovery of function in athletes with patellar tendinopathy. Participants were volleyball, hand-ball and basketball players with symptoms of patellar tendinopathy for a minimum of 3 to a maximum duration of 12 months and who were still able to train and compete. The intervention group received three patient-guided focussed medium-energy density ESWT treatments without local anaesthesia at a weekly interval in the first half of the competition. The control group received placebo treatment. The follow-up measurements took place 1, 12 and 22 weeks after the final ESWT or placebo treatment, when athletes were still in competition. Primary outcome measure was the VISA-P (Victorian Institute of Sport Assessment - patella) score. Data on pain during function tests (jump tests and single-leg decline squat) and ultrasound characteristics were also collected. During the follow-up period participants also registered pain, symptoms, sports participation, side effects of treatment and additional medical consumption in an internet-based diary.Chapter 8 reports the results and main outcome of the TOPGAME study. A total of 127 symptomatic athletes were invited to participate; 62 were eligible, gave consent and were randomised into the ESWT (n=31) or placebo group (n=31). Mean VISA-P scores before and 1, 12 and 22 weeks after treatment were 59.4 (±11.7), 66.8 (±16.2), 66.7 (±17.5) and 70.5 (±18.9) for the ESWT group and 62.4 (±13.4), 66.3 (±19.0), 68.9 (±20.3) and 72.7 (±18.0) for the placebo group. There was a significant effect for time (p<0.01), but no treatment x time interaction effect (p=0.82). Secondary outcome measures showed the same. From these findings it was concluded that ESWT as single treatment during the competitive season has no benefit over placebo treatment in the management of actively competing jumping athletes with patellar tendinopathy who have symptoms for less than 12 months.The general discussion in Chapter 9 presents the research described in the previous chapters in a broader perspective and puts forward clinical implications and suggestions for further research. The first part of the chapter describes the epidemiology of patellar tendinopathy in athletes and its implications for prevention. The second part of this gen-eral discussion focuses on the different assessment tools that might be used as outcome measures for patellar tendinopathy. In the third part the role of ESWT, amongst other treatment options, in the management of patellar tendinopathy is discussed. The contin-uum model of tendon pathology is presented, which may help to understand and explain the variable success rate of different treatment options. Further research is needed to determine the optimal treatment strategy for patellar tendinopathy.

Appendix A

Nederlandse samenvatting

Nederlandse samenvatting 135

De patellatendinopathie (ook wel jumper’s knee genoemd) is een veel voorkomende en lastig te behandelen overbelastingsblessure van de patellapees die de carrière van een sporter vaak sterk negatief beïnvloedt. Er lijkt sprake van een gestoord regeneratiepro-ces in de pees en niet van een ontsteking zoals eerder gedacht werd, wat consequenties heeft voor de te volgen behandelstrategie. Centraal in een revalidatieprogramma voor patellatendinopathie staan aangepaste belasting, excentrische oefentherapie gericht op verbetering van de spier-peesfunctie en het optimaliseren van de belastbaarheid. Peesh-erstel gaat langzaam, waardoor langdurige revalidatie nodig is. Anti-inflammatoire be-handelmethoden zijn meestal niet succesvol. Chirurgisch ingrijpen biedt ook geen ga-rantie voor een snelle symptoomloze terugkeer in de sport op het oorspronkelijke niveau. Extracorporele shockwavetherapie (ESWT), het echoscleroseren van neovascularisaties en tendineuze en peritendineuze injecties met aprotinine en autologe groeifactoren lijken nieuwe, veelbelovende behandelmethoden.Dit proefschrift richt zich op het vergoten van de huidige kennis betreffende de patel-latendinopathie bij recreatieve sporters en de rol die ESWT in de behandeling van deze aandoening kan spelen. Het eerste doel is om te beschrijven wat de prevalentie is van de patellatendinopathie bij breedtesporters en wat mogelijke risicofactoren zijn voor deze overbelastingsblessure. Het tweede doel is om specifieke evaluatiemethodes voor de pa-tellatendinopathie te ontwikkelen en te onderzoeken. Het derde doel is om de effectiviteit van ESWT als behandelmethode voor de patellatendinopathie te bestuderen.Het doel van de studie beschreven in hoofdstuk 3 was om vast te stellen wat de preval-entie van patellatendinopathie is onder recreatieve sporters en verder om potentiële risi-cofactoren voor deze aandoening te vinden. Daarom werden 891 vrouwelijke en manneli-jke recreatieve sporters van zeven populaire sporten in Nederland (basketbal, volleybal, handbal, korfbal, voetbal, hockey en atletiek) bevraagd. Door middel van een speciaal ontwikkelde vragenlijst werd informatie verkregen met betrekking tot individuele karak-teristieken (leeftijd, lengte, gewicht), trainingsachtergrond, eerdere en huidige knieproble-men en de VISA-P (Victorian Institute of Sport Assessment - Patella) score als maat voor ernst van de blessure. De totale prevalentie van de patellatendinopathie was 8,5% (78 van de 891 sporters), waarbij er een significant verschil was tussen de sporten die verschil-len in de mate van belasting van de knie en de ondergrond waarop gespeeld wordt. De prevalentie was het hoogst onder volleyballers (14,4%) en het laagst onder voetballers (2,5%), en significant hoger onder mannelijke sporters (51 van de 502, 10,2%) dan onder vrouwelijke sporters (25 van de 389, 6,4%). De gemiddelde duur van de klachten was 18,9 maanden (SD 21,6; range 2,0–59,8). De gemiddelde VISA-P van de sporters met patellaten-dinopathie was 71,4 (SD 13,8). Sporters met patellatendinopathie waren significant ouder, langer en zwaarder dan sporters zonder patellatendinopahtie. Op grond van de resultaten van deze cross-sectionele survey kan geconcludeerd worden dat de prevalentie van de patellatendinopathie ook onder recreatieve sporters hoog is en dat de patellatendinopa-thie bijna tweemaal zoveel voorkomt bij mannelijke als bij vrouwelijke recreatiesporters. Verschillende sportspecifieke belastingskarakteristieken van het strekapparaat van de knie, ondergrond waarop gespeeld wordt, en leeftijd, lengte en gewicht lijken factoren die geassocieerd zijn met de patellatendinopathie. De VISA-P vragenlijst kwantificeert de ernst van de klachten, de kniefunctie en de mogeli-jkheid om te sporten bij sporters met een patellatendinopathie. Deze korte Engelstalige

136 Nederlandse samenvatting

vragenlijst die door de sporters zelf wordt ingevuld, is in Australië ontwikkeld om de revalidatie te monitoren en de resultaten van klinische studies te evalueren. Het doel van hoofdstuk 4 was om deze vragenlijst volgens internationale richtlijnen te vertalen naar het Nederlands en om de reproduceerbaarheid en validiteit van deze Nederlandstalige versie van de VISA-P te onderzoeken. Om de test-hertest betrouwbaarheid te bepalen vulden 99 studenten de vragenlijst 2 keer in, met een tijdsinterval van 2,5 weken. Om de discriminatieve validiteit van de Nederlandse VISA-P te onderzoeken, vulden 18 gezonde studenten, 15 prestatiegerichte volleyballers (‘at-risk’ populatie), 14 patiënten met een pa-tellatendinopathie, 6 patiënten die geopereerd waren vanwege een patellatendinopathie, 17 patiënten met een andere knieblessure dan patellatendinopathie, en 9 patiënten met niet-knie gerelateerde klachten de Nederlandse VISA-P in. De Nederlandstalige VISA-P vragenlijst liet een acceptabele test-hertest betrouwbaarheid zien (ICC = 0,74). De gemiddelde (± SD) VISA-P scores waren 95 (± 9) voor de gezonde studenten, 89 (± 11) voor de volleyballers, 58 (± 19) voor patiënten met een patellatendi-nopathie en 56 (± 21) voor sporters die een operatie vanwege een patellatendinopathie aan hun knie hadden ondergaan. Patiënten met een andere knieblessure dan patellaten-dinopathie en patiënten met niet-knie gerelateerde klachten scoorden respectievelijk 62 (± 24) en 77 (± 24) punten. Uit deze studie kan geconcludeerd worden dat de Nederland-se VISA-P vragenlijst een betrouwbare en valide scoringsmethode is om symptomen, kniefunctie en mogelijkheid om te kunnen sporten te evalueren bij Nederlandse sporters met patellatendinopathie.De single-leg squat op een helling van 25° is zowel een klinisch bruikbare belastingstest als een oefentherapeutische interventie voor patiënten met een patellatendinopathie. Er bestaan verschillende hypotheses ten aanzien van de belasting op de patellapees en de patellofemorale krachten tijdens de single-leg squat, maar deze zijn nooit onderzocht in biomechanische studies. Daarom was het doel van de studie beschreven in hoofdstuk 5 om te onderzoeken hoe de kniemomenten en patellofemorale krachten zich verhouden tot de hellingshoek bij de single-leg squat. Vijf proefpersonen voerden op een been ex-centrische squats uit onder een hellingshoek van 0°, 5°, 10°, 15°, 20° en 25°, zonder en met een 10-kg zware rugzak, en onder een hellingshoek van 30° op een helling die op een krachtplaat was geplaatst. Kinematische en krachtplaat data werden vastgelegd met het Optotrak systeem. Gewrichtsmomenten van enkel, knie en heup werden berekend met behulp van twee-dimensionale inverse dynamica. Het kniemoment nam met 40% toe bij hellingshoeken van 15° en hoger, terwijl enkel- en heupmoment afnamen. De maxi-male knie- en enkelhoeken namen toe bij steilere hellingshoeken. Met 10kg extra gewicht, onder een hellingshoek van 25° was het knie moment 23% hoger dan onbelast. Zowel de krachten in de patellapees als de patellofemorale krachten namen toe bij hogere helling-shoeken maar vanaf 60% knieflexie namen de patellofemorale krachten meer toe dan die in de patellapees. Uit dit onderzoek kan geconcludeerd worden dat alle op een been uitge-voerde squats onder een hellingshoek van meer dan 15° resulteren in een 40% toename van de maximale patellapees kracht. Bij een knieflexie van meer dan 60° nemen de patel-lofemorale krachten meer toe dan de krachten in de patellapees. Een hogere belasting op de pees kan bereikt worden door extra gewicht in een rugzak te gebruiken.De literatuurreview beschreven in hoofdstuk 6 vat de huidige kennis met betrekking tot ESWT als behandelmethode voor de patellatendinopathie samen. Het doel van deze

Nederlandse samenvatting 137

review was om (1) de effectiviteit van ESWT als behandeling voor de patellatendinopa-thie te onderzoeken, (2) richtlijnen op te stellen voor een effectief ESWT behandelprotocol voor de patellatendinopathie, en (3) nieuwe onderzoeksgebieden voor verdere studies te vinden. Een systematische en geautomatiseerde zoekopdracht in de Medline en Embase databases werd uitgevoerd om studies te vinden die de effectiviteit van ESWT op de pa-tellatendinopathie beschrijven. Er werden zeven studies over dit onderwerp geïncludeerd, allemaal gepubliceerd na 2000. Deze studies omvatten in totaal 283 patiënten (298 pezen), waarvan er 204 (215 pezen) behandeld werden met ESWT. De behandelresultaten waren positief, maar de meeste studies hadden methodologische tekortkomingen, kleine patiën-tenaantallen en/of korte follow-up periodes. De methode van opwekken en applicatie van de shockwaves, het gebruikte energieniveau, het aantal en de frequentie van de behan-delingen, het gebruik van (lokale) anesthesie en lokalisatiemethode varieerden. Op basis van deze review kan geconcludeerd worden dat ESWT een veilige en veelbelovende be-handeling lijkt te zijn voor de patellatendinopathie met een positief effect op pijn en func-tie. Op grond van de huidige kennis is het echter onmogelijk een specifiek behandelproto-col aan te bevelen. Verder basaal en klinisch onderzoek naar de het werkingsmechanisme en de effectiviteit van ESWT bij de patellatendinopathie zijn nodig.Hoofdstuk 7 beschrijft de studieopzet van de TOPGAME studie (Tendinopathy of Patella Groningen Amsterdam Maastricht ESWT), die als doel heeft om de effectiviteit van ESWT te bepalen bij sporters met een patellatendinopathie die ondanks pijn door-trainen en wedstrijden spelen. De TOPGAME studie is de eerste gerandomiseerde ge-controleerde studie met geblindeerde deelnemers en beoordelaars, die het effect onder-zoekt van gefocuste ESWT op pijnreductie en herstel van functie bij sporters met een patellatendinopathie in vergelijking met sporters die placebo-ESWT krijgen. Deelnemers waren volleyballers, handballers en basketballers met patellatendinopathie klachten van tenminste 3 en maximaal 12 maanden die wel in staat waren om te blijven trainen en wedstrijden te spelen. De interventiegroep werd in de eerste competitiehelft 3 maal met een tijdsinterval van een week behandeld met door feedback van de patiënt gestuurde gefocuste ESWT met gemiddelde energiedichtheid zonder lokaal anesthesie. De controlegroep kreeg een pla-cebo- ESWT behandeling. De follow-up metingen werden 1, 12 en 22 weken na de laatste ESWT of placebo-ESWT behandeling verricht, waarbij de laatste meting nog binnen het speelseizoen viel. De primaire uitkomstmaat was de VISA-P score. Ook werden gegevens verzameld over pijn tijdens functietesten (sprongtesten en single-leg decline squat). Ge-durende de hele follow-up periode registreerden de deelnemers via internet in een logboek ook de mate van pijn, klachten, sportbeoefening, bijwerkingen van de behandeling en eventuele bijkomende medische behandelingen. Hoofdstuk 8 rapporteert de belangrijkste resultaten van de TOPGAME studie. In to-taal 127 sporters werden uitgenodigd om deel te nemen aan de studie; 62 voldeden aan de inclusiecriteria en werden na toestemming gerandomiseerd in een ESWT (n=31) of een placebogroep (n=31). De gemiddelde VISA-P scores voor en 1, 12, en 22 weken na behandeling waren 59,4 (±11,7), 66,8 (±16,2), 66,7 (±17,5) en 70,5 (±18,9) voor de ESWT groep en 62,4 (±13,4), 66,3 (±19,0), 68,9 (±20,3) en 72,7 (±18,0) voor de placebogroep. Er was een significant effect voor tijd (p<0,01), maar geen behandeling x tijd interactie effect (p=0,82). De secundaire uitkomstmaten lieten hetzelfde patroon zien. Op grond van deze

138 Nederlandse samenvatting

resultaten is de conclusie dat ESWT als monotherapie geen voordeel heeft ten opzichte van placebobehandeling bij de behandeling van actief doorsportende sporters met een patellatendinopathie met klachten korter dan 12 maanden.De algemene discussie in hoofdstuk 9 plaatst de resultaten van de studies uit de voor-gaande hoofdstukken in een breder perspectief. Daarbij worden tevens klinische aan-bevelingen en suggesties voor verder onderzoek gedaan. In het eerste deel worden de epidemiologie van de patellatendinopathie en de implicaties voor preventie van deze aandoening beschreven. Het tweede deel van de algemene discussie focust op de verschil-lende evaluatiemethodes die gebruikt kunnen worden als uitkomstmaat voor de patel-latendinopathie. In het derde deel wordt de rol van ESWT, temidden van andere behande-lopties, in de behandeling van de patellatendinopathie beschreven. Het “peespathologie continuüm model” wordt gepresenteerd waarmee het mogelijk wordt beter te begrijpen en te verklaren waarom de resultaten van verschillende behandelmethodes zo divers zijn. Verder onderzoek is nodig om de optimale behandelstrategie te bepalen voor de patel-latendinopathie.

Appendix B

VISA-P questionnaire

142 VISA-P questionnaire

The VISA-P questionnaire in English

Name: _______________________________ Date: ___ ________

The Victorian Institute of Sport Assessment Score

1. For how many minutes can you sit pain free?

0 – 15 mins

15 – 30 mins

30 – 60 mins

60 – 90 mins

90 – 120 mins

> 120 mins

0 2 4 6 8 10

2. Do you have pain walking downstairs normally? No

painSevere Pain / Unable

0 1 2 3 4 5 6 7 8 9 10

3. Do you have pain at the knee with full active non-weight bearing knee extension?

No pain

Severe Pain / Unable

0 1 2 3 4 5 6 7 8 9 10

4. Do you have pain when doing a lunge?

No pain

Severe Pain / Unable

0 1 2 3 4 5 6 7 8 9 10

5. Do you have problems when squatting? No

painSevere Problems / Unable

0 1 2 3 4 5 6 7 8 9 10

6. Do you have pain during or immediately after doing 10 single leg hops? No

painSevere Pain / Unable

0 1 2 3 4 5 6 7 8 9 10

VISA-P questionnaire 143

7. Are you currently undertaking all aspects of normal training or activity?

0 No. Not at all.

4 Modified training or activity.

7 Full training / competition but not at same level as when symptoms began.

10 Competing at the same level as symptoms began.

8. This question has 3 parts - please answer one part only

If you have no pain while being active or playing sport → answer Q8a only. If you have pain while active or playing sport but it doesn’t stop you from training → answer Q8b only. If you have pain that stops you from being active or playing sport → answer Q8c only.

8a. If you have no pain while playing sport, for how long do you train?

0 – 20 mins

20 – 40 mins

40 – 60 mins

60 – 90 mins

> 90 mins

6 12 18 24 30

8b. If you have some pain while playing sport, but it does not stop you from completing your training, for how long can you train?

0 – 15 m ins

15 – 30 mins

30 – 45 mins

45 – 60 mins

> 60 mins

0 5 10 15 20

8c. If you have pain that stops you from playing sport, for how long can you train?

Nil

0 – 10 mins

10 – 20 mins

20 – 30 mins

> 30 mins

0 2 5 7 10

TOTAL VISA SCORE

--

-

Appendix C

Nederlandse

VISA-P vragenlijst

146 VISA-P vragenlijst

J. Zwerver, T. Kramer, I. van den Akker-Scheek 2009

De Nederlandse VISA-P score

Naam: Geboortedatum:

Datum:

1. Hoeveel minuten kunt u zitten zonder pijn?

0 – 15 minuten

15 – 30 minuten

30 – 60 minuten

60 – 90 minuten

90 – 120 minuten

> 120 minuten

0 2 4 6 8 10

2. Hebt u pijn als u de trap afloopt in een normaal tempo?

Geen pijn

Hevige pijn of niet mogelijk 0 1 2 3 4 5 6 7 8 9 10

3. Hebt u pijn als u uw knie strekt zonder er gewicht op te zetten?

Geen pijn


4. Hebt u pijn wanneer u een uitvalspas (lunge) maakt?

Geen pijn


5. Hebt u problemen met het uitvoeren van de squatbeweging (hurkbeweging)?

Geen pijn


6. Hebt u pijn gedurende of direct na het doen van 10 sprongetjes/hupjes op één been?

Geen pijn


The translated Dutch VISA-P questionnaire

VISA-P vragenlijst 147

J. Zwerver, T. Kramer, I. van den Akker-Scheek 2009

7. Doet u op dit moment aan sport of andere fysieke activiteiten?

0 Helemaal niet

4 Aangepaste training en/of aangepaste competitie

7 Volledige training en/of competitie, maar niet op hetzelfde niveau als toen de symptomen begonnen

10 Op hetzelfde wedstrijdniveau of op een hoger wedstrijdniveau in vergelijking met het begin van de symptomen

8. Vult u alstublieft of A, of B of C in bij deze vraag- Wanneer u geen pijn hebt tijdens het sporten beantwoordt dan alleen vraag 8A.- Als u pijn hebt tijdens het sporten , maar u hoeft niet te stoppen met de sportieve

activiteit, beantwoordt dan alleen vraag 8B. - Wanneer u zodanige pijn hebt dat u moet stoppen met de sportieve activiteit,

beantwoordt dan alleen vraag 8C.

8a. Wanneer u geen pijn hebt tijdens het sporten, hoe lang kunt u dan trainen?

0 – 20 minuten

20 – 40 minuten

40 – 60 minuten

60 – 90 minuten

> 90 minuten

6 12 18 24 30

8b. Wanneer u pijn hebt tijdens het sporten, maar u hoeft hierdoor niet te stoppen met sporten, hoe lang kunt u dan trainen?

0 – 15 minuten

15 – 30 minuten

30 – 45 minuten

45 – 60 minuten

> 60 minuten

0 5 10 15 20

8c. Wanneer u een zodanige pijn hebt dat u moet sto ppen met trainen, hoe lang kunt u dan trainen?

Niet 0 – 10 minuten

10 – 20 minuten

20 – 30 minuten

> 30 minuten

0 2 5 7 10

TOTALE SCORE

Appendix D

Dankwoord

Dankwoord 151

Beste Ron, ik wil je bedanken voor de mogelijkheid die je me gegeven hebt om vanuit het Sportmedisch Centrum UMCG deze promotiestudie te verrichten. Je liet me de ruimte om mijn gang te gaan en had vertrouwen in een goede afloop. Op de schaarse momenten in dit traject dat er wat hobbels op de weg waren, stond je op en effende je adequaat het pad. Naar mijn idee is het echter vrij gladjes verlopen en is het grootste obstakel waar je in de afgelopen drie jaar mee geconfronteerd werd mijn brievenbus geweest. Gelukkig kon je (bumper) daar prima tegen. Dankjewel voor je hulp en het in mij gestelde vertrouwen!

Beste Inge, zonder jou was dit proefschrift niet tot stand gekomen. Jouw geweldige inzet, je ongelooflijke werklust en niet aflatende steun waardeer ik zeer. We voelden elkaar per-fect aan en ik kon altijd bij je aankloppen; niet alleen voor allerlei onderzoeksgerelateerde vragen die bij mij “als simpele sportarts” opkwamen, maar ook om even te mopperen of voor een (of meestal meerdere) dropjes. Heel hartelijk bedankt!

Beste Fred, als sportarts heb je een belangrijke rol gespeeld in het design, de uitvoering en de rapportage van de TOPGAME studie en afronding van deze thesis. Jouw positieve kritische commentaar, punctualiteit en soms verfrissende Limburgse kijk zijn heel nuttig geweest en hebben beslist bijgedragen aan het slagen van dit project. Dankjewel!

Beste Frank, Sjoerd en Koen, graag wil ik jullie als leden van de leescommissie bedanken voor het kritisch doorlezen en beoordelen van het manuscript.

Beste Steef, jij haalde mij in 2002 naar Groningen om 2e sportarts te worden in het toen-malige AZG. Ik heb je sindsdien leren kennen als een zeer gemotiveerde, inspirerende en vakbekwame collega die sportgeneeskunde hoog in het vaandel heeft. Je initieerde negen jaar geleden het jumper’s knee onderzoek. Jouw flair heeft mij geïnspireerd om groter te denken op onderzoeksgebied, wat onder meer resulteerde in de landelijke TOPGAME studie. Je soms vlijmscherpe analyses maar altijd positieve feedback zijn nuttig geweest voor dit proefschrift. Daarnaast stond je op de werkvloer altijd klaar als ik soms afwezig was. Kortom je bent een geweldige collega! Dankjewel!

Beste Hans, als “tweedehansje” heb jij een zeer belangrijke rol gespeeld in de TOPGAME studie. Jij zorgde ervoor dat de praktische zaken vlot verliepen, had contact met de deelne-mers en stuurde het TOPGAME team aan. Als ik zenuwachtig rondrende en me afvroeg of alles goed geregeld was, straalde jij altijd rust uit en stond iedereen vriendelijk te woord. Ook buiten het werk ben ik deze rust en vriendelijkheid van je gaan waarderen. Ik heb prettig met je samen gewerkt en wil je heel hartelijk bedanken voor je geweldige bijdrage aan dit project.

Beste Nynke, ook jij bent zeer belangrijk geweest voor het slagen van de TOPGAME studie. Hoewel de onderzoekswereld helemaal nieuw en misschien wel wat vreemd voor je was, legde je op enthousiaste wijze de basis voor het succes door onder meer je com-municatie met de bonden en sporters en door het ontwikkelen van de website. Dat je en passant ook nog een prachtige zoon (potentiële volleyballer?) op aarde zette is natuurlijk helemaal een TOP prestatie. Dankjewel!

152 Dankwoord

Natuurlijk wil ik het hele TOPGAME team bedanken dat geholpen heeft bij dit project. Zonder jullie geweldige steun was dit niet gelukt. Evert, dankjewel voor je methodologi-sche ondersteuning; Lydia en Tetske, dank voor jullie geweldige inzet en bereidheid om letterlijk door weer en wind, stad en land af te reizen en deelnemers achter de broek aan te zitten voor de behandeling en evaluatie; Henk, jou wil ik specifiek bedanken voor de data analyses en het meedenken. Ik ga ervan uit dat je op passende wijze een vervolg geeft aan dit onderzoek en er dan zelf op promoveert; Gerard, dank voor je hulp op locatie Twente; Alex, Joris, Patrick, Robert, Toine en Yvonne dank voor jullie bijdrage in regio Zuid; dank ook aan alle studenten die enthousiast geholpen hebben bij de metingen. De TOPGAME studie was niet mogelijk geweest zonder de (financiële) steun van ZonMw en de logistieke ondersteuning door de NEVOBO, NBB, NHV. Hartelijk dank hiervoor! Last but not least wil ik alle “proefpersonen” bedanken voor hun bereidheid om deel te nemen aan de TOP-GAME studie en de tijd die zij er ook ingestoken hebben.

Zonder de illusie te hebben compleet te zijn en niet iemand te vergeten (sorry!) zijn er nog een aantal mensen die ik wil bedanken. In de eerste plaats alle collega’s op het Sportme-disch Centrum UMCG: Annemarieke, Anton, Bea, Bram, Corry, Elvira, Feikje, Ida, Jan, Jannie, Klaus, Leon, Marco, Marieke, Marcus, Marianne, Martin, Monique, Patrick, Rienk, Ronald, Sjoerdina en Stijn. Op onderzoeksgebied heb ik veel geleerd van en plezier beleefd aan de contacten met de “bewegingswetenschappers” At, Esther, Gert Jan, Koen, Martin, Mathijs, Michel, Paul en Pieter. In het tendinopathie-onderzoek hebben Femke, Jeroen, Marije, Robert, Ruben, Saskia en Tamara en nog vele andere (student)onderzoekers een be-langrijke bijdrage geleverd. Pepijn, jouw rol in de ontwikkeling van de musculo-skeletale echografie is voor het peesonderzoek van onschatbare waarde geweest. Ronald, jij stond altijd klaar voor het vriendelijk beantwoorden van al die kleine tussendoor vraagjes op gebied van ICT, powerpoint, filmpjes en foto’s. Het af en toe aanschuiven bij de lunch met alle sporten orthopedie onderzoekers was voor mij vaak een welkome onderbreking van een drukke werkdag. Ook de contacten met en de feedback van de andere peesonderzoek-ers binnen de Nederlandse TENDON groep, zijn nuttig geweest voor het tot stand komen van dit proefschrift. Ik realiseer me dat ik de afgelopen jaren het voorrecht heb gehad om prettig met jullie te mogen samenwerken. Dank aan jullie allemaal!

Het is me de afgelopen jaren meer en meer duidelijk geworden dat zelfs ik een promotie-traject niet alleen kan doen. Steun uit je directe omgeving is daarbij ontzettend belang-rijk.

Beste Mirjam en Jan, dank voor jullie bereidheid om af en toe bij te springen als ik van-wege mijn onderzoek weg moest.

Lieve Corrie en Henk, beste Menno en lieve Gerry, hartelijk dank voor jullie luisterend oor, steun en de inzichtgevende gesprekken op de momenten, dat het nodig was.

Lieve Papa en lieve mama, het waren niet de makkelijkste jaren maar mijn “werkstuk” is af. Fijn dat jullie af en toe konden oppassen en me bleven steunen. Zonder de degelijk gemaakte decline boards was het niet gelukt, papa! Bedankt!

Dankwoord 153

Lieve Ylva en lieve Olav, papa is eindelijk klaar met “het boekje”. Jullie hadden gelijk, ik heb per dag meer uren achter de computer gezeten (en minder buiten gespeeld) dan jullie. Toch waren jullie altijd nieuwsgierig naar “het boekje” en wilden jullie het zelfs sponsoren. Geweldig! Jullie belangrijkste bijdrage voor mij is echter dat jullie er zijn. En van nu af aan ben ik er ook weer helemaal voor jullie!

Lieve, lieve Marlies, ik hoop dat jij dit proefschrift en alles wat er mee te maken heeft (gehad) zo snel mogelijk vergeet. Jij hebt er namelijk al meer dan genoeg over gehoord. Onthoud alsjeblieft alleen de allerbelangrijkste conclusie die in dit proefschrift staat: ik houd heel veel van jou en wil samen met jou gelukkig jong blijven!

Appendix E

Curriculum Vitae

Curriculum Vitae 157

Johannes Zwerver (roepnaam Hans) werd geboren op 3 september 1967 in Emmeloord. Na het doorlopen van het Gymnasium aan de C.S.G. te Emmeloord, studeerde hij ge-zondheidswetenschappen (propedeuse) en geneeskunde aan de Katholieke Universiteit Nijmegen. Naast zijn studie speelde hij basketbal op (inter)nationaal niveau.Na zijn artsexamen (1994) vervulde hij zijn diensplicht als bataljonsarts te Ede. In 1996 begon hij zijn opleiding tot sportarts met stages orthopedie en cardiologie in het Canisius Wilhelmina Ziekenhuis in Nijmegen. Vervolgens werkte hij als sportarts in opleiding bij het Sportmedisch Centrum Papendal en bij SGA Sanasport in Nijmegen. Van 1997 tot 2000 was hij daarnaast clubarts bij NEC en nadien teamarts bij Eiffeltowers Basketbal. Na afronden van zijn specialisatie bleef hij werken bij SGA Sanasport en SMC Papendal en was hij waarnemend sportarts bij diverse sportmedische instellingen. Daarnaast ver-zorgde hij de medische begeleiding van diverse sportteams en –bonden.Sinds eind 2002 is hij als sportarts werkzaam bij het Sportmedisch Centrum UMCG in Groningen alwaar hij betrokken is bij patiëntenzorg, onderwijs en onderzoek. Zijn re-search activiteiten richten zich met name op de (patella)tendinopathie en op het overtrain-ingssyndroom.

Appendix F

List of publications

160 List of publications

Zwerver J, Hartgens F, Verhagen E, van den Akker-Scheek I, Diercks RL. No Effect of Extracorporeal Shockwave Therapy on Patellar Tendinopathy in Jumping Athletes during the Competitive Season: a randomized clinical trial. Am J Sports Med. Accepted pending revisions.

Zwerver J, Dekker F, Pepping GJ. Patient guided Piezo-electric Extracorporeal Shockwave Therapy as treatment for chronic severe patellar tendinopathy: A pilot study. J Back Musculoskelet Rehabil. 2010;23(3):111-5.

Brink MS, Visscher C, Arends S, Zwerver J, Post WJ, Lemmink KA. Monitoring stress and recovery: new insights for the prevention of injuries and illnesses in elite youth soccer players. Br J Sports Med. 2010;44(11):809-15. Zwerver J, Verhagen E, Hartgens F, van den Akker-Scheek I, Diercks RL. The TOPGAME-study: effectiveness of extracorporeal shockwave therapy in jumping athletes with patellar tendinopathy. Design of a randomised controlled trial. BMC Musculoskelet Disord. 2010 Feb 8;11:28.

Zwerver J. Sportblessures in de huisartspraktijk: de springersknie. Modern Medicine. 2010;34(1):21-23.

Zwerver J. Boekbespreking “Sportgeneeskunde” onder redactie van Baarveld, Backx en Voorn. Ned Tijdschr Geneeskd. 2009;153:A1107.

Zwerver J, Kramer T, van den Akker-Scheek I. Validity and reliability of the Dutch translation of the VISA-P questionnaire for patellar tendinopathy. BMC Musculoskelet Disord. 2009 Aug 11;10(1):102.

Zwerver J. Epidemiologie van sportletsels. In: Cursusboek Postgraduate course revalidatie geneeskunde. Onder redactie van Geertzen JHB, Martina JD, Zahavi BAA. ISBN/EAN 978-90-74768-41-2. p 36-41.

Zwerver J. Inspanningstolerantie tijdens sporten door gehandicapten. In: Cursusboek Postgraduate course revalidatie geneeskunde. Onder redactie van Geertzen JHB, Martina JD, Zahavi BAA. ISBN/EAN 978-90-74768-41-2. p 45-6.

Zwerver J. Sporttraining en oefentherapie: overeenkomsten? In: Cursusboek Postgraduate course revalidatie geneeskunde. Onder redactie van Geertzen JHB, Martina JD, Zahavi BAA. ISBN/EAN 978-90-74768-41-2. p 47-51.

Van Leeuwen MT, Zwerver J, van den Akker-Scheek I. Extracorporeal Shockwave Therapy for Patellar Tendinopathy; a review of the literature. Br J Sports Med. 2009;43(3):163-8.

List of publications 161

Zwerver J. Revalidatie van de knie; een praktische leidraad voor de behandeling van deze blessure. In: Als pijn chronisch wordt. Onder redactie van Nijs J, van Wilgen CP. Standaard Uitgeverij, Antwerpen. 2009. p 137-57.

Zwerver J, Slagers AJ. Diagnostiek en behandeling van de jumper’s knee. In: Jaarboek Fysiotherapie/Kinesitherapie 2009. Onder redactie van Geraets J.J.X.R et al. Bohn Stafleu Van Loghum, Houten. 2009. p 72-87.

Nederhof E, Zwerver J, Brink M, Meeusen R, Lemmink K. Different diagnostic tools in nonfunctional overreaching. Int J Sports Med. 2008;29(7):590-7.

Zwerver J. [Patellar tendinopathy (‘jumper’s knee’); a common and difficult-to-treat sports injury] Ned Tijdschr Geneeskd. 2008;152(33):1831-7.

Zwerver J, Bessem B, Buist I, Diercks RL.[The value of preventive advice and examination focusing on cardiovascular events and injury for novice runners]Ned Tijdschr Geneeskd. 2008;152(33):1825-30.

Bisseling RW, Hof AL, Bredeweg SW, Zwerver J, Mulder T. Are the takeoff and landing phase dynamics of the volleyball spike jump related to patellar tendinopathy? Br J Sports Med. 2008;42(6):483-9.

Zwerver J, Bredeweg SW, Hof AL. Biomechanical analysis of the single-leg decline squat. Br J Sports Med. 2007;41(4):264-8. Discussion 268.

Nederhof E, Lemmink K, Zwerver J, Mulder T. The Effect of High Load Training on Psychomotor Speed. Int J Sports Med. 2007;28(7):595-601.

Buist I, Bredeweg SW, Lemmink KA, Pepping GJ, Zwerver J, van Mechelen W,Diercks RL. The GRONORUN study: is a graded training program for novice runners effective in preventing running related injuries? Design of a Randomized Controlled Trial. BMC Musculoskelet Disord. 2007 Mar 2;8:24.

Bisseling RW, Hof AL, Bredeweg SW, Zwerver J, Mulder T. Relationship between landing strategy and patellar tendinopathy in volleyball. Br J Sports Med. 2007;41(7):e8.

Nederhof E, Lemmink KA, Zwerver J, Meeusen R. Reaction time as a possible marker for overtraining syndrome.Geneeskunde en Sport. 2006;39:230-3.

162 List of publications

Slagers AJ, Zwerver J. Patellaire tendinopathie. In: Fysiotherapeutische Casuïstiek. Onder redactie van Dekker, Takken en Witvrouw (BSL), mei 2005.

De Greef M, Zwerver H, Boers E, De Boer E, Vestering M. The validity of personal activity monitor (PAM) acceleration meters to measure physical activity of overweight women. Geneeskunde en Sport. 2004;37(3):71-4.

Zwerver J, Folgering HThM. The reproducibility of hand-held dynamometry in patients with lung function disorders. Geneeskunde en Sport. 2000;33(4):23-30.

Zwerver J, Witteveen AGH, van Dijk CN. “Sinus Tarsi syndroom” bij een profvoetballer. In: Sporttraumatologische Casuïstiek. Onder redactie van RJ van Heerwaarden en MP Heijboer, februari 2000.

Zwerver J, Heere LP. The hamstring syndrome and other peripheral causes of sciatica. Geneeskunde en Sport. 1999;32(2):5-8.

Ellis ML, Zwerver J. Is een afneembaar spicaverband na elke primaire totale heuparthroplastiek zinvol? Ned Tijdschr Orthop. 1998;5:14-7.

Zwerver J, Rieu PNMA, Koopman RJJ, Spauwen PHM, Buskens FGM, Boetes C, Veth RPH, Van Oostrom CG. Vascular malformations: A review of 10 years’ management in a university hospital. Pediatr Surg Int. 1996;11(5-6):296-300.

Appendix G

List of (inter)national presentations

166 List of (inter)national presentations

Zwerver J, van den Akker-Scheek I, Hartgens F, van der Worp H, Verhagen E, Diercks RL. No Effect of Extracorporeal Shockwave Therapy in Jumping Athletes with Patellar Tendinopathy; a randomized controlled trial. Annual Meeting International Society for Musculoskeletal Shockwave Therapy, June 2010, Chicago, USA.

Van der Worp H, Zwerver J, van den Akker-Scheek I. ESWT treatment protocols for jumper’s knee: a survey among ISMST members. Annual Meeting International Society for Musculoskeletal Shockwave therapy, June 2010, Chicago, USA.

Zwerver J, van den Akker-Scheek I, Hartgens F, van der Worp H, Verhagen E, Diercks RL. The TOPGAME study: Effectiveness of Extracorporeal shockwave therapy in jumping athletes with patellar tendinopathy; a randomized controlled trial. ESSKA Congress, June 2010, Oslo, Norway.

Zwerver J, van den Akker-Scheek I, Verhagen E, van der Worp H, Hartgens F, Diercks RL. Effectiveness of Extracorporeal shockwave therapy in active athletes with patellar tendinopathy; a randomized controlled trial. Annual Meeting American College of Sports Medicine, June 2010, Baltimore, USA.

Zwerver J, van der Worp H, Hartgens F, Verhagen E, van den Akker-Scheek I, , Diercks RL. The TOPGAME study; No effect of ESWT in Jumping Athletes with patellar tendinopathy; a RCT. Annual Meeting Nederlandse Vereniging voor Arthroscopie, May 2010, Noordwijk aan Zee.

Zwerver J. Shockwave therapie en de “Jumper’s knee”. Scientific Meeting Impuls, May 2010, Houten.

Zwerver J, van den Akker-Scheek I, Verhagen E, van der Worp H, Hartgens F, Diercks RL. Effectiveness of Extracorporeal shockwave therapy in active athletes with patellar tendinopathy; a randomized controlled trial. SHARE Scientific meeting, May 2010, Groningen.

Zwerver J. De TOPGAME studie en ander patella tendinopathie onderzoek. Research symposium UCSBG, April 2010, Groningen.

Zwerver J. De TOPGAME-studie: een RCT naar de effectiviteit van ESWT bij actieve sporters met een patellatendinopathie. VSG Scientific Congress, December 2009, Noordwijkerhout(Award: Prijs voor Sport en Orthopedie 2009; 3d best abstract)

Willemse L, Zwerver J, van den Akker-Scheek I. De diagnostische validiteit van verschillende assessment tools bij patellatendinopathie (jumper’s knee). VSG Scientific Congress, December 2009, Noordwijkerhout

List of (inter)national presentations 167

Noord R van, Zwerver J, van Wilgen CP. Test-hertest betrouwbaarheid van de pressure pain treshold en de VAS-30 bij patiënten met een jumper’s knee. VSG Scientific Congress, December 2009, Noordwijkerhout

Zwerver J. Etiological factors associated with patellar tendinopathy. TENDON Meeting. May 2009 MCH Leidschendam

Zwerver J. Pathofysiologie Tendinopathie; is behandeling met ESWT geïndiceerd? Congress Podotherapie. Innovatieve toepassingen binnen de voetzorg, April 2009, Bilthoven.

Zwerver J, van Leeuwen M, van den Akker-Scheek. ESWT for Patellar Tendinopathy; a review of the literature. Annual Meeting International Society for Musculoskeletal Shockwave Therapy, April 2009, Sorrento, Italy.

Zwerver J. De jumper’s knee; een lastig te behandelen sportblessure. Symposium “Knikkende knieën”. Regionaal Genootschap Fysiotherapie Het Noorden. Themadag March 2009, Heerenveen.

Zwerver J. Patellatendinopathie: lopend onderzoek en de TOPGAMEstudie. Dutch Tendon Group. VSG Scientific Congress. November 2008, Noordwijkerhout.

Kramer T, Zwerver J, van den Akker-Scheek I. De betrouwbaarheid en validiteit van de Nederlandse VISA-P vragenlijst. VSG Scientific Congress, November 2008, Noordwijkerhout.(Award: Prijs voor Sport, Bewegen en Gezondheid 2008; best abstract)

Leeuwen van MT, Zwerver J, van den Akker-Scheek I. Extracorporele schokgolftherapie voor de patellapees tendinopathie, een review van de literatuur. VSG Scientific Congress, November 2008, Noordwijkerhout.

Verburg H, Zwerver J, van den Akker-Scheek I. De prevalentie van de springersknie bij niet professionele handballers. VSG Scientific Congress, November 2008, Noordwijkerhout.

Roerink SD, Zwerver J, van den Akker-Scheek I. Etiologische factoren van de patellatendinopathie; een review. VSG Scientific Congress, November 2008, Noordwijkerhout.(Award: Prijs voor Sport, Bewegen en Gezondheid 2008; 2nd best abstract)

Eijzeren v J, Zwerver J, van den Akker-Scheek I. Extracorporele shockwave therapie in de behandeling van de Achillespees tendinopathie; een review van de literatuur. VSG Scientific Congress, November 2008, Noordwijkerhout.


Vries de J, Zwerver J. Tendinopathie en genetica. VSG Scientific Congress, November 2008, Noordwijkerhout.

Brink MS, Zwerver J, Lemmink K. Hormonale reactie op dubbele maximale inspanning als kenmerk van overtraindheid. VSG Scientific Congress, November 2008, Noordwijkerhout.

Zwerver J. Tendinopathieen: een update.VRA meeting, Sport en Bewegen, June 2008, Utrecht.

Zwerver J. Work-up and non-surgical treatment of tendon pathology. Congress NVA/NOTS/VS, March 2008, Ermelo.

Huisjes M, Greef de MHG, Kuchenbecker W, Zwerver J. Effect van leefstijlinterventieprogramma WOW! op subfertiliteit bij vrouwen met overgewicht; de eerste resultaten. VSG Scientific Congress, November 2007, Noordwijkerhout.(Award: Prijs voor Sport, Bewegen en Gezondheid 2007; best abstract)

Haan de W, Pepping GJ, Zwerver J. Kwantificering van palpatiepijn bij de jumper’s knee met behulp van een Hand-Held Dynamometer. VSG Scientific Congress, November 2007, Noordwijkerhout.

Dekker F, Pepping GJ, Zwerver J. Effectiviteit van Extracorporele Shockwave Therapie (ESWT) als behandeling voor sporters met een chronische patellatendinopathie. VSG Scientific Congress, November 2007, Noordwijkerhout.

Nederhof E, Lemmink KAPM, Zwerver J. Stress-regeneration and reaction times in overtraining diagnosis. European Congress of Sport Psychology, Sept 2007, Hakidiki, Greece.

Zwerver J. Tendinopathies in soccer; new concepts to treat. Congress “Soccer Science in Motion”, June 2007, Heerenveen.

Zwerver J. Patella tendinopathie, een update. Sportmedicine Congress “Het strekapparaat van de knie”, April 2007, Baarn.

Zwerver J. Schokgolftherapie bij tendinopathieen. Workshop 5th Groningen Sports Medicine Symposium, January 2007, Groningen.

Zwerver J. Echogeleid scleroseren bij tendinopathieen. Workshop 5th Groningen Sports Medicine Symposium, January 2007, Groningen.

List of (inter)national presentations 169

Zwerver J, Hamelink JLC, Slagers AJ, Dijkstra PU. Diagnostiek en behandeling van de jumper’s knee: een cross-sectionele survey onder Nederlandse sportartsen en sportfysiotherapeuten. VSG Scientific Congress, December 2006, Noordwijkerhout.

F. Dekker, J. Zwerver, G.J. Pepping. Effectiviteit van Patient-Guided Focused Extracorporeal Shockwave Therapie bij recreatieve sporters met een chronische Fasciitis Plantaris: een pilotstudie. VSG Scientific Congress, December 2006, Noordwijkerhout.

Zwerver J, Bredeweg SW. Prevalence of jumper’s knee among non-elite athletes from 3 different sports (poster). Scientific Meeting FIMS, June 2006, Beijing, China.

Bredeweg SW, Buist I, Zwerver J, Van Mechelen W, Diercks RL. Does a modified training program prevent running injuries? First results from a RCT. Scientific Meeting FIMS, June 2006, Beijing, China.

Zwerver J. Behandeling van Chronische tendinopathieën (in de sport). Scientific Meeting VvBN, 2006, Groningen.

Nederhof E, Lemmink KAPM, Zwerver J, Meeusen R. The Influence of High Load Training on Reaction Time in Cyclists.Annual Meeting American College of Sports Medicine, May 2006, Denver, Colorado, USA.

Zwerver J. Eccentric training in Tendinopathy. VSG Scientific Congress, December 2005, Noordwijkerhout.

Nederhof E, Lemmink KAPM, Zwerver J, Visscher C, Meeusen R, Mulder ThW. Overtraining Syndrome: Psychomotor speed as an early marker. VSG congres 2 december 2005, Noordwijkerhout

Nederhof E, Lemmink KAPM, Zwerver J, Meeusen R. Psychomotor speed is a possible marker for overreaching. Annual Congress European College of Sports Science, July 2005, Belgrado, Serbia.

Nederhof E, Lemmink KAPM, Zwerver J. Cognitive speed and selective attention: Possible markers for overtraining? Annual Congress European College of Sports Science, July 2004, Clermont Ferrand, France.

Zwerver J, Folgering HThM. Hand-held dynamometrie: handig in de revalidatie? VSG Scientific Meeting, November 1999, Bilthoven.


Hopman MTE, Zwerver J, van Norel GJ. The effect of wearing a CTI2 brace on walking economy and leg-muscle properties. Annual Meeting American College of Sports Medicine, June 1997, Denver, USA.

Hopman MTE, Zwerver J, van Norel GJ. Het effect van een CTI2 brace op loopefficiëntie, spierkracht en spiervermoeidheid bij patiënten met een instabiele knie en controles. Meeting NOV, October 1996, Nieuwegein.

Zwerver J, Spauwen PHM, Rieu PNMA. Vasculaire Anomalieën van de Bovenste Extremiteit. Nederlandse Vereniging voor Handchirurgie, May 1994, Utrecht.

Appendix H

Onderwijs en overige activiteiten

174 Onderwijsactiviteiten

Begeleiding

Sportarts in opleiding (Plaatsvervangend opleider UMCG)

Huisarts in opleiding tijdens stages sportgeneeskunde

Studenten en co-assistenten UMCG tijdens stage sportgeneeskunde

Studenten geneeskunde en studenten bewegingswetenschappen bij onderzoeksstages (RUG)

Begeleiding studenten fysiotherapie en medische beeldvormende techniek bij onderzoeksstages (Hanzehogeschool)

Colleges

Sports Medicine and Overuse injuries. 2e jaars Studenten International Bachelor Medicine Global Health RUG. 16 september 2010, Groningen.

Tendinopathy. 2e jaars Studenten International Bachelor Medicine Global Health RUG. 16 september 2010, Groningen.

Tendinopathie en tendinose. 3e jaars Studenten Geneeskunde RUG. 20 oktober 2009, Groningen.

Sportmedische begeleiding. 3e jaars Studenten Fysiotherapie HanzeHogeschool Gezondheidstudies. 21 februari 2009, Groningen.


De Sportarts en sportgeneeskunde. 1e jaars Studenten Geneeskunde RUG. 16 september 2008, Groningen.

Sportmedische begeleiding. 3e jaars Studenten Fysiotherapie HanzeHogeschool Gezondheidstudies. 18 juni 2008, Groningen.


Onderwijsactiviteiten 175

Onderwijsbijeenkomsten

Diagnostiek en behandeling van de Tendinopathie. AGIOS Orthopedie UMCG. 17 februari 2010, Groningen.

Onderzoek van het bewegingsapparaat. Bewegingstweedaagse HAIOS UMCG. 26 januari 2010, Groningen.

Tendinopathie: nieuwe inzichten. Onderwijsprogramma Revalidatie OOR Noord-Oost Nederland. 11 september 2009, Enschede.

Wat is sportgeneeskunde? Disciplinecaroussel Studenten geneeskunde 1e jaars. 1 september 2009, Groningen.

Epidemiologie van sportletsels. Postgraduate course revalidatie geneeskunde NASKHO. 17 mei 2009, Curaçao.

Inspanningstolerantie tijdens sporten door gehandicapten. Postgraduate course revalidatie geneeskunde NASKHO. 17 mei 2009, Curaçao.

Sporttraining en oefentherapie: overeenkomsten? Postgraduate course revalidatie geneeskunde NASKHO. 17 mei 2009, Curaçao.

Aandoeningen van heup, bovenbeen en lies. Bewegingstweedaagse HAIOS UMCG. 20 januari 2009, Groningen.

Diagnostiek en behandeling van de Tendinopathie. AGIOS Radiologie UMCG. 27 oktober 2008, Groningen.

Workshop Tendinopathie onderzoek. Noordelijk Coach platform TSN. 16 oktober 2008, Groningen.

Update tendinopathie, onderwijsbijeenkomst HAIOS UMCG. 14 augustus 2008, Groningen.

Diagnostiek en behandeling van de Tendinopathie. AGIOS Orthopedie UMCG. 23 april 2008, Groningen.

Inleiding Trainingsfysiologie Werkgroep deskundigheidsbevordering Huisartsen Zuid-oost Drenthe. 18 en 25 september 2007, Emmen.

Tendinopathieen, een update. Opleidingsdag Orthopedie, regio Noord-Oost. 23 mei 2007, Groningen.

Recente ontwikkelingen bij Chronische Achillespeesklachten. Nascholingsbijeenkomst

Regionaal Genootschap voor Fysiotherapie Groot Ysselland. Maart 2007, Hoogeveen en Zwolle.

Bewegen op recept. 18e Drentse Nascholingscursus Huisartsen. Maart 2007, de Lutte.

176 Onderwijsactiviteiten

Lezingen

Overbelastingsletsels. Symposium Transplantatie en sport. 17 september 2010, UMCG Groningen.

Overbelasting en peesblessures in de sport. Medische publieksacademie UMCG (i.s.m. Dagblad van het Noorden). 9 maart 2010, Groningen.

De jumper’s knee: van lab tot TOPGAME. Invitational conference LOSO. 25 november 2009, Utrecht.

Mentale en fysieke gevolgen van bewegen. Themadag Bewegen en sporten bij pijn. 6 november 2009, Revalidatiecentrum UMCG/Beatrixoord. Haren

Peesblessures. Sportgeneeskunde in de wetenschappelijke praktijk: van sportveld tot kliniek. Symposium voor sportverzorgers, trainers en studenten. 7 oktober 2009, UMCG Groningen.

Sportmedische begeleiding van de beklimming van de Alpe d’Huez. Clinic voor deelnemers. 4 februari 2009, Marum.

Tendinopathie onderzoek. Onderzoekssymposium UCSBG. 30 september 2008, UMCG Groningen.

Women of weight with infertility. Onderzoekssymposium UCSBG. 30 september 2008, UMCG Groningen.

Shockwavetherapie: internationaal wetenschappelijk onderzoek; een update. Innovatie seminar Gymna Uniphy. 25 september 2008, Nuland.

Overgewicht, subfertiliteit en bewegen. Informatiebijeenkomst WOW-project gynaecologie. 24 april 2007, UMCG Groningen.

Overbelastingsblessures. Refereeravond hardlooptrainers. 12 maart 2007, Groningen.

Schokgolf therapie. Studentencongres Kapot van Sport. 16 februari 2006, Groningen.

Sportmedische begeleiding. Belcampo college (LOOT-school). 20 december 2005, Groningen.

Onderwijsactiviteiten 177

Overige activiteiten

ReviewerAmerican Journal of Sports MedicineBritish Journal of Sports MedicineClinical RheumatologyNederlands tijdschrift voor GeneeskundeSport en Geneeskunde

WerkgroepWerkgroep VSG/CBO: multidisciplinaire richtlijn Iliotibiaal BandsyndroomWerkgroep Consument en Veiligheid: preventie van sportblessuresMedeoprichter TENDON: multicenter werkgroep Tendinopathie Onderzoek Nederland Symposiumcommissie Groningen Sports Medicine Symposium

Relevante Opleidingen

2007 Teach the teacher (Wenckebach)2008 Instructional Course Musculoskeletal Ultrasound (Medipoint)2009 Masterclass Tendinopathy (NPI)

Appendix I

SHARE

180 SHARE

Groningen Graduate School of Medical Sciences – Research Institute SHARE

This thesis is published within the research program Public Health Research (PHR) of the Research Institute SHARE of the Groningen Graduate School of Medical Sciences (embedded in the University Medical Center Groningen / University of Groningen). More information regarding the institute and its research can be obtained from our internetsite: www.rug.nl/share.

Previous dissertations from the program Public Health Research

Hoedeman R (2010) Severe medically unexplained physical symptoms in a sick-listed occupational health populationSupervisor: prof dr JW GroothoffCo-supervisors: dr B Krol, dr AH Blankenstein

Bieleman A (2010) Work participation and work capacity in early osteoarthritis of the hip and the kneeSupervisor: prof dr JW GroothoffCo-supervisors: dr FGJ Oosterveld, dr MF Reneman

Spanjer J (2010) The Disability Assessment Structured Interview; its reliability and validity in work disability assessmentSupervisor: prof dr JW GroothoffCo-supervisors: dr B Krol, dr S Brouwer

Koopmans PC (2009) Recurrence of sickness absence; a longitudinal studySupervisor: prof dr JW GroothoffCo-supervisor: dr CAM Roelen

Chang CMS (2009) Ageing with joy; the effect of a physical education programme on the well-being of older peopleSupervisors: prof dr JR van Horn, prof dr JW Groothoff, prof dr MA VreedeCo-supervisor: dr M Stevens

Krokavcová M (2009) Perceived health status in multiple sclerosis patientsSupervisor: prof dr JW GroothoffCo-supervisors: dr JP van Dijk, dr I Nagyová, dr Z Gdovinová, dr LJ Middel

SHARE 181

El-Sayed Hussein El-Baz N (2009) Effect of clinical pathway implementation and patients’ characteristics on outcomes of coronary artery bypass graft surgerySupervisor: prof dr SA ReijneveldCo-supervisors: dr LJ Middel, dr JP van Dijk, dr PW Boonstra

Buitenhuis J (2009) The course of whiplash; its psychological determinants and consequences for work disabilitySupervisors: prof dr JW Groothoff, prof dr PJ de JongCo-supervisor: dr JPC Jaspers

Santvoort MM van (2009) Disability in Europe; policy, social participation and subjective well-beingSupervisor: prof dr WJA van den HeuvelCo-supervisors: dr JP van Dijk, dr LJ Middel

Stewart RE (2009) A multilevel perspective of patients and general practitionersSupervisors: prof dr B Meyboom-de Jong, prof dr TAB Snijders, prof dr FM Haaijer-Ruskamp

Jong J de (2009) The GALM effect study; changes in physical activity, health and fitness of sedentary and underactive older adults aged 55-65Supervisor: prof dr EJA Scherder Co-supervisors: dr KAPM Lemmink, dr M Stevens

Buist I (2008) The GronoRun study; incidence, risk factors, and prevention of injuries in novice and recreational runnersSupervisors: prof dr RL Diercks, prof dr W van MechelenCo-supervisor: dr KAPM Lemmink

Škodová Z (2008) Coronary heart disease from a psychosocial perspective: socioeconomic and ethnic inequalities among Slovak patientsSupervisor: prof dr SA ReijneveldCo-supervisors: dr JP van Dijk, dr I Nagyová, dr LJ Middel, dr M Studencan

Havlíková E (2008) Fatigue, mood disorders and sleep problems in patients with Parkinson’s diseaseSupervisor: prof dr JW GroothoffCo-supervisors: dr JP van Dijk, dr J Rosenberger, dr Z Gdovinová, dr LJ Middel

Bos EH (2008) Evaluation of a preventive intervention among hospital workers to reduce physical loadSupervisor: prof dr JW GroothoffCo-supervisor: dr B Krol

182 SHARE

Wagenmakers R (2008) Physical activity after total hip arthroplastySupervisors: prof dr S Bulstra, prof dr JW GroothoffCo-supervisors: dr M Stevens, dr W Zijlstra

Zuurmond RG (2008) The bridging nail in periprosthetic fractures of the hip; incidence, biomechanics, histology and clinical outcomesSupervisor: prof dr SK BulstraCo-supervisors: dr AD Verburg, dr P Pilot

Wynia K (2008) The Multiple Sclerosis Impact Profile (MSIP), an ICF-based outcome measure for disability and disability perception in MS: development and psychometric testingSupervisors: prof dr SA Reijneveld, prof dr JHA De Keyser Co-supervisor: dr LJ Middel

Leeuwen RR van (2008) Towards nursing competencies in spiritual careSupervisors: prof dr D Post, prof dr H Jochemsen Co-supervisor: dr LJ Tiesinga

Vogels AGC (2008) The identification by Dutch preventive child health care of children with psychosocial problems : do short questionnaires help?Supervisors: prof dr SA Reijneveld, prof dr SP Verloove-Vanhorick

Kort NP (2007) Unicompartmental knee arthroplastySupervisor: prof dr SK BulstraCo-supervisors: dr JJAM van Raay, dr AD Verburg

Akker-Scheek I van den (2007) Recovery after short-stay total hip and knee arthroplasty; evaluation of a support program and outcome determinationSupervisors: prof dr JW Groothoff, prof dr SK BulstraCo-supervisors: dr M Stevens, dr W Zijlstra

Mei SF van der (2007) Social participation after kidney transplantationSupervisors: prof dr WJA van den Heuvel, prof dr JW Groothoff, prof dr PE de JongCo-supervisor: dr WJ van Son

Khan MM (2007) Health policy analysis: the case of PakistanSupervisors: prof dr WJA van den Heuvel, prof dr JW GroothoffCo-supervisor: dr JP van Dijk

Rosenberger J (2006) Perceived health status after kidney transplantationSupervisors: prof dr JW Groothoff, prof dr WJA van den HeuvelCo-supervisors: dr JP van Dijk, dr R Roland

SHARE 183

Šléškova M (2006) Unemployment and the health of Slovak adolescentsSupervisors: prof dr SA Reijneveld, prof dr JW GroothoffCo-supervisors: dr JP van Dijk, dr A Madarasova-Geckova

Dumitrescu L (2006) Palliative care in RomaniaSupervisor: prof dr WJA van den Heuvel

The B (2006) Digital radiographic preoperative planning and postoperative monitoring of total hip replacements; techniques, validation and implementationSupervisors: prof dr RL Diercks, prof dr JR van HornCo-supervisor: dr ir N Verdonschot

Jutte PC (2006) Spinal tuberculosis, a Dutch perspective; special reference to surgerySupervisor: prof dr JR van Horn Co-supervisors: dr JH van Loenhout-Rooyackers, dr AG Veldhuizen

Leertouwer H (2006) Het heil van de gezonden zij onze hoogste wet; de geschiedenis van de medische afdeling bij de arbeidsinspectieSupervisors: prof dr JW Groothoff, prof dr MJ van Lieburg, prof dr D Post

Jansen DEMC (2006) Integrated care for intellectual disability and multilpe sclerosisSupervisors: prof dr D Post, prof dr JW GroothoffCo-supervisor: dr B Krol

Ham I van (2006) De arbeidssatisfactie van de Nederlandse huisartsSupervisors: prof dr J de Haan, prof dr JW GroothoffCo-supervisor: dr KH Groenier

Jansen GJ (2005) The attitude of nurses towards inpatient aggression in psychiatric care: the development of an instrument Supervisors: prof dr SA Reijneveld, prof dr ThWN Dassen Co-supervisor: dr LJ Middel

Post M (2005) Return to work in the first year of sickness absence; an evaluation of the Gatekeeper Improvement ActSupervisors: prof dr JW Groothoff, prof dr D PostCo-supervisor: dr B Krol

Landsman-Dijkstra JJA (2005) Building an effective short healthpromotion intervention; theory driven development, implementation and evaluation of a body awareness program for chronic a-specific psychosomatic symptomsSupervisor: prof dr JW GroothoffCo-supervisor: dr R van Wijck

184 SHARE

Bakker RH (2005) De samenwerking tussen huisarts en bedrijfsartsSupervisor: prof dr JW GroothoffCo-supervisors: dr B Krol, dr JWJ van der Gulden

Nagyová I (2005) Self-rated health and quality of life in Slovak rheumatoid arthritis patientsSupervisor: prof dr WJA van den HeuvelCo-supervisor: dr JP van Dijk

Gerritsma-Bleeker CLE (2005) Long-term follow-up of the SKI knee prosthesis.Supervisors: prof dr JR van Horn, prof dr RL DiercksCo-supervisor: dr NJA Tulp

Vries M de (2005) Evaluatie Zuidoost-Drenthe HARTstikke goed!; mogelijkheden van community-based preventie van hart-en vaatziekten in NederlandSupervisors: prof dr D Post, prof dr JW GroothoffCo-supervisor: dr JP van Dijk

Jungbauer FHW (2004) Wet work in relation to occupational dermatitisSupervisors: prof dr PJ Coenraads, prof dr JW Groothoff

Post J (2004) Grootschalige huisartsenzorg buiten kantoorurenSupervisor: prof dr J de Haan

Reneman MF (2004) Functional capacity evaluation in patients with chronic low back pain; reliability and validitySupervisors: prof dr JW Groothoff, prof dr JHB Geertzen Co-supervisor: dr PU Dijkstra

Bâra-Ionilã C-A (2003) The Romanian health care system in transition from the users’ perspectiveSupervisors: prof dr WJA van den Heuvel, prof dr JAM Maarse Co-supervisor: dr JP van Dijk

Lege W de (2002) Medische consumptie in de huisartspraktijk op UrkSupervisors: prof dr D Post, prof dr JW Groothoff

Hoekstra EJ (2002) Arbeidsbemiddeling met behulp van Supported Employment als interventie bij de reïntegratie van chronisch zieken; de rol van de arbeidsbemiddelaar, chronisch zieke en werkgeverSupervisors: prof dr JW Groothoff, prof dr K Sanders, prof dr WJA van den Heuvel, prof dr D Post

SHARE 185

Enk JG van (2002) Determinants of use of healthcare services in childhoodSupervisors: prof dr D Post, prof dr AJP Veerman, prof dr WJA van den Heuvel

Gecková A (2002) Inequality in health among Slovak adolescentsSupervisors: prof dr D Post, prof dr JW Groothoff Co-supervisor: dr JP van Dijk

Dijk JP van (2001) Gemeentelijk gezondheidsbeleid; omvang en doelgerichtheidSupervisors: prof dr D Post, prof dr M Herweijer, prof dr JW Groothoff

Middel LJ (2001) Assessment of change in clinical evaluationSupervisor: prof dr WJA van den Heuvel Co-supervisor: dr MJL de Jongste

Bijsterveld HJ (2001) Het ouderenperspectief op thuiszorg; wensen en behoeften van ouderen ten aanzien van de thuis(zorg)situatie in FrieslandSupervisors: prof dr D Post, prof dr B Meyboom-de Jong Co-supervisor: dr J Greidanus

Dijkstra GJ (2001) De indicatiestelling voor verzorgingshuizen en verpleeghuizenSupervisors: prof dr D Post, prof dr JW Groothoff

Dalen IV van (2001) Second opinions in orhopaedic surgery: extent, motives, and consequencesSupervisors: prof dr JR van Horn, prof dr PP Groenewegen, prof dr JW Groothoff

Beltman H (2001) Buigen of barsten? Hoofdstukken uit de geschiedenis van de zorg aan mensen met een verstandelijke handicap in Nederland 1945-2000Supervisors: prof dr D Post, prof dr AThG van Gennep

Pal TM (2001) Humidifiers disease in synthetic fiber plants: an occupational health studySupervisors: prof dr JGR de Monchy, prof dr D Post, prof dr JW Groothoff

Goossen WTF (2000) Towards strategic use of nursing information in the NetherlandsSupervisors: prof dr WJA van den Heuvel, prof dr ThWN Dassen, prof dr ir A Hasman

Hospers JJ (1999) Allergy and airway hyperresponsiveness: risk factors for mortalitySupervisors: prof dr D Post, prof dr DS Postma, prof dr ST Weiss

186 SHARE

Wijk P van der (1999) Economics: Charon of Medicine? Supervisors: prof dr WJA van den Heuvel, prof dr L Koopmans, prof dr FFH Rutten Co-supervisor: dr J Bouma

Dijkstra A (1998) Care dependency: an assessment instrument for use in long-term care facilitiesSupervisors: prof dr WJA van den Heuvel, prof dr ThWN DassenTuinstra J (1998) Health in adolescence: an empirical study of social inequality in health, health risk behaviour and decision making stylesSupervisors: prof dr D Post, prof dr WJA van den Heuvel Co-supervisor: dr JW Groothoff

Mink van der Molen AB (1997) Carpale letsels: onderzoek naar de verzuimaspecten ten gevolgen van carpale letsels in Nederland 1990-1993Supervisors: prof dr PH Robinson, prof WH Eisma Co-supervisors: dr JW Groothoff, dr GJP Visser

Mulder HC (1996) Het medisch kunnen: technieken, keuze en zeggenschap in de moderne geneeskundeSupervisor: prof dr WJA van den Heuvel

Dekker GF (1995) Rugklachten-management-programma bij de Nederlandse Aardolie Maatschappij B.V.: ontwerp, uitvoering en evaluatieSupervisors: prof dr D Post, prof WH Eisma Co-supervisor: dr JW Groothoff

Puttiger PHJ (1994) De medische keuring bij gebruik van persluchtmaskersSupervisors: prof dr D Post, prof dr WJA Goedhard Co-supervisor: dr JW Groothoff

Engelsman C & Geertsma A (1994) De kwaliteit van verwijzingen Supervisors: prof dr WJA van den Heuvel, prof dr FM Haaijer-Ruskamp, prof dr B Meyboom-de Jong

Lucht F van der (1992) Sociale ongelijkheid en gezondheid bij kinderenSupervisor: prof dr WJA van den Heuvel Co-supervisor: dr JW Groothoff

Acknowledgements

The TOPGAME study was funded by the Netherlands Organisation for Health Research and development (ZonMW), grant number 750.20.010.

Wolf GmbH (Knittlingen, Germany) supported the TOPGAME study by providing the ESWT devices.

The NBB, NEVOBO and NHV gave logistic support toward contacting the athletes during the TOPGAME study.

Printing of this thesis was financially supported by:

BauerfeindBiometGlaxoSmithKlineGymnaUniphy

Nea InternationalOIM OrthopedieOrthinOtto Bock Benelux Oudshoorn Chirurgische techniek Penders Voetzorg

Tramedico

Centrum voor Revalidatie (UMCG)

Nederlandse Orthopaedische Vereniging (NOV)NVMST Impuls

Their support is gratefully acknowledged!

Arthrex Nederland B.V.

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