Ed INVITED REVIEW

Scapular dyskinesis: the surgeon’sperspective

Simon J Roche1, Lennard Funk2, Aaron Sciascia3 andW Ben Kibler3

AbstractThe scapula fulfils many roles to facilitate optimal function of the shoulder. Normal function of the shoulder joint requires

a scapula that can be properly aligned in multiple planes of motion of the upper extremity. Scapular dyskinesis, meaning

abnormal motion of the scapula during shoulder movement, is a clinical finding commonly encountered by shoulder

surgeons. It is best considered an impairment of optimal shoulder function. As such, it may be the underlying cause or the

accompanying result of many forms of shoulder pain and dysfunction. The present review looks at the causes and

treatment options for this indicator of shoulder pathology and aims to provide an overview of the management of

disorders of the scapula.

Keywords

Dyskinesis, instability, scapula

Date received: 17th June 2015; accepted: 22nd June 2015

Introduction

Normal scapula function is essential for optimal shoul-der function in all individuals and, in particular, theoverhead throwing athlete. Scapula control and pos-itioning allows for optimal positioning of the humerusin relation to the glenoid transferring power from thecore to the distal upper extremity. Abnormalities ofscapula function can be seen in many patients. It pre-sents clinically as asymmetry in scapular motion com-pared to the contralateral side, either in elevation ordescent, leading to a disrupted motion.

In a static sense, it may present as a prominence ofthe scapula or a resting position of protraction com-pared to the other side. Scapular dyskinesis can bedefined as a collective term that refers to movementof the scapula that is dysfunctional and may create apossible impairment of overall shoulder function,although it may also represent the cause of persistentshoulder symptoms or may be the manifestation ofunderlying structural shoulder pathology in manytypes of shoulder injury.1 In this review, we explorecontemporary concepts in the understanding and man-agement of scapular dyskinesis from the surgeon’sperspective.

Anatomical concepts of the scapula

The scapula is attached to the axial skeleton via theclavicle through the acromioclavicular (AC) and ster-noclavicular joints. It has muscular attachments to theposterior aspect of the ribcage via trapezius, rhomboidsand serratus anterior. Core strength is transferred viathe glenohumeral joint to the arm and hand by optimalcoupling of the muscle activations and bony motion.The scapula has relatively limited bony attachmentsand is therefore dependent on mostly muscle activationfor mobility and stability.

Normal movement of the scapula comprises compo-nents of three motions: (i) upward/downward rotationaround a horizontal axis perpendicular to the plane ofthe scapula; (ii) internal/external rotation around a

1Royal Oldham Hospital, Oldham, UK2Wrightington Hospital, Wigan, UK3Lexington Clinic, Lexington, KY, USA

Corresponding author:

Lennard Funk, Wrightington Hospital, Hall Lane, Appley Bridge, Wigan

WN6 9EP, UK.

Tel: þ44 1625 545071Email: lenfunk@shoulderdoc.co.uk

Shoulder & Elbow

2015, Vol. 7(4) 289–297

! The Author(s) 2015

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vertical axis through the plane of the scapula; and(iii) anterior/posterior tilt around a horizontal axis inthe plane of the scapula. The clavicle acts as a strut forthe shoulder complex, connecting the scapula to theaxial skeleton. Normality of this linkage enables twotranslations: (i) upward/downward translation on thethoracic wall and (ii) retraction/protraction aroundthe rounded thorax (Figure 1).2,3

The coupling of scapular external rotation, posteriortilt, upward rotation and medial translation is calledretraction. The coupling of internal rotation, angulartilt, downward rotation and lateral translation iscalled protraction. The coupling of upward translation,anterior tilt and internal rotation is seen as a shrug.1

The scapula fulfils important functions in dynamicand static modes. In addition to upward rotation, thescapula is required to tilt posteriorly and externallyrotate to clear the acromion from the moving arm inelevation and abduction. In addition, the scapula mustbe able to internally/externally rotate in a synchronousmanner to maintain the glenoid as a congruent socketfor the arm in motion, thereby maximizing concavitycompression and ball and socket kinematics. The scap-ula must be dynamically stabilized in a position of

retraction during use of the arm to achieve maximalactivation of all of the muscles that originate on thescapula.4,5

Another important role of the scapula in the normalshoulder is as a link in the proximal to distal sequencingof velocity, energy and forces of shoulder function. Inmost cases, sequencing begins at ground level and indi-vidual body segments are coordinated by muscle acti-vation and body position to generate, summate andtransfer forces through these segments to the terminallink. This sequence is termed the kinetic chain.6

The upper and lower trapezius muscles in addition tothe serratus anterior muscles have been shown to be thegreatest contributors to scapular stability and mobility(Figure 2).5,7 The trapezius and serratus anterior mus-cles initiate upward rotation and posterior tilt of thescapula. Activation of the lower trapezius muscleplays an important role in the stability of the arm inthe overhead position and in descent of the arm from aposition of maximum elevation. The rhomboids assistthe trapezius in stabilizing the scapula contributing tocontrol of medial and lateral scapular translation.Latissimus dorsi and pectoralis minor, which are bothextrinsic shoulder girdle muscles, affect scapular

Figure 1. Combined translational movements of the scapula in three planes lead to protraction and retraction around the thorax.

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motion in their role as prime movers of the arm. Thesemuscles act mainly as force couples. The appropriateforce couples for scapular stabilization include theupper and lower portions of the trapezius muscle work-ing together with the rhomboid muscles, paired with theserratus anterior muscle (Figure 3).8 The appropriateforce couples for acromial elevation are the lower tra-pezius and the serratus muscles working together pairedwith the upper trapezius and rhomboid muscles.6

Scapular dyskinesis

Scapular dyskinesis (alteration of motion) is a term thatdenotes loss of control of normal scapular motion,physiology or mechanics. Dyskinesis as opposed to dys-kinesia is the more accurate terminology because thelatter is applied to abnormal active movementsmediated by neurological factors (e.g. tardive dyskin-esia), whereas dyskinesis is more inclusive, incorporat-ing many other factors that may be causative.1

Dyskinesis as a finding in the examination of theshoulder may be the result of an injury, although itmay also not be related to any form of previoustrauma. The clinical characteristics may include prom-inence of the medial or inferomedial scapular border,early scapular elevation or shrugging on arm elevationand/or rapid downward rotation on lowering of thearm.9 The efficacy of shoulder function is altered inmany ways, with resulting changes in 3D glenohumeralangulation, AC joint strain, subacromial space dimen-sions, maximal muscle activation and optimal arm pos-ition and motion. This may result in augmentation ofpre-existing symptoms related to concurrent shoulderpathology or produce new symptoms of pain/discom-fort where none existed previously.

There are multiple causes of dyskinesis. Joint-relatedcauses include high-grade AC arthrosis and instabilityand glenohumeral joint internal derangement. Bonycauses include thoracic kyphosis, clavicular fracturenon-union and clavicular malunion with shortening,

Figure 2. Prime movers and stabilizers of the scapula: upper and lower trapezius with serratus anterior.

Ed Roche et al. 291

rotation or angulation. Neurological causes includepalsies of the long thoracic or spinal accessory nervesand cervical radiculopathy.

The commonest causative mechanisms of dyskinesishave a soft tissue components, involving either intrinsicmuscle pathology or inflexibility or inhibition of normalmuscle activation. Decreased flexibility of either theshort head of biceps muscle or pectoralis minor havebeen shown to create anterior tilt and protraction ofthe scapula as a result of their pull on the coracoid.10

Periscapular muscle activation alterations may beseen in patients with dyskinesis. Strength and activationof serratus anterior are reduced in cases of impingement

and shoulder pain. This can cause a loss of posterior tiltand upward rotation of the scapula leading to scapulardyskinesis.11

Regardless of the particular cause of dyskinesis, thefinal result in most cases is a protracted scapula eitherat rest or with the arm in motion. Protraction is notfavourable for optimal shoulder function and results indecreased subacromial space with increased symptomsof impingement and increased extrinsic rotator cuffcompression. Rotator cuff strength can also bedecreased.4,5 Protraction can also lead to an increasein strain of the anterior glenohumeral ligaments and agreater risk of internal impingement.12

Figure 3. Force couples for scapula motion: in early elevation (a, b), the upper and lower trapezius and serratus anterior muscles

have long lever arms, being effective rotators and stabilizers. With higher arm elevation (c), the upper trapezius moment arm is

shorter, whereas the lower trapezius and serratus anterior moment arms remain long, continuing to rotate the scapula. With

maximum arm elevation (d), the lower trapezius maintains scapula position and the instant centre of rotation moves from

the medial border of the spine to the acromioclavicular joint (adapted from Bagg SD, Forrest W).8

292 Ed Shoulder & Elbow 7(4)

Scapular dyskinesis and specific shoulder injuries

Labral injury. Scapular dyskinesis has a high associationwith labral injury.13 The altered position and motion ofinternal rotation and anterior tilt changes GH align-ment, placing increased tensile strain on the anteriorligaments, increasing ‘peel-back’ of the biceps/labralcomplex on the glenoid, and creating pathologicalinternal impingement. These effects are magnified inthe presence of glenohumeral internal rotation deficit,which creates increased protraction as a result of ‘wind-up’ of the tight posterior structures in follow-through.The demonstration of dyskinesis in patients with sus-pected labral injury provides a key component ofrehabilitation protocols. Correction of the symptomsof pain found in the modified dynamic labral sheartest14 can be frequently demonstrated by the additionof manual scapular retraction. This indicates the pres-ence of dyskinesis as part of the pathophysiology andthe need for scapular rehabilitation to improve scapularretraction, including mobilization of tight anterior mus-cles and institution of the scapular stability series ofstrengthening exercises.

Impingement. Impingement is frequently seen in throw-ing athletes. Most commonly in this group, impinge-ment is secondary to other pathology such asinstability, labral injury or biceps pathology. Scapulardyskinesis is associated with impingement by alteringthe scapular position at rest and upon dynamic motion.Scapular dyskinesis in impingement is characterized byloss of acromial upward rotation, excessive scapularinternal rotation and excessive scapular anteriortilt.15,16 These positions create scapular protraction,which decreases the subacromial space and decreasesdemonstrated rotator cuff strength.4,17

Activation sequencing patterns and strength of themuscles that stabilize the scapula are altered in patientswith impingement and scapular dyskinesis. Increasedupper trapezius activity, imbalance of upper trapez-ius/lower trapezius activation, such that the lower tra-pezius activates later than normal, and decreasedserratus anterior activation have been reported inpatients with impingement.15 Increased upper trapeziusactivity is clinically observed as a shrug manoeuvre,resulting in a variation of the scapular dyskinesis pat-tern. This causes impingement as a result of a lack ofacromial elevation. Frequently, lower trapezius activa-tion is inhibited or delayed, creating impingementbecause of loss of acromial elevation and posteriortilt. Serratus anterior activation has been shown to bedecreased in patients with impingement, creating a lackof scapular external rotation and elevation with armelevation.

The pectoralis minor has been shown to be shor-tened in length in patients with impingement.

This tight muscle creates a position of scapular protrac-tion at rest and does not allow scapular posterior tilt orexternal rotation upon arm motion, predisposingpatients to impingement symptoms.

Rotator cuff injury. The rotator cuff is frequently clinicallyinvolved in throwers with shoulder symptoms andsymptoms can be exacerbated by dyskinesis. The dys-kinetic position that results in an internally rotated andanteriorly tilted glenoid increases the internal impinge-ment on the posterior superior glenoid with arm exter-nal rotation and increases the torsional twisting of therotator cuff, which may create the undersurface rotatorcuff injuries seen in throwers.12 In addition, positions ofscapular protraction have been shown to be limiting tothe development of maximal rotator cuff strength.Recent work in laboratory models of rotator cuff dis-ease has shown that surgically induced scapular dyskin-esis results in changes in cell morphology, geneexpression and tendon characteristics that are similarto those seen in rotator cuff tendinopathy.18

AC joint injuries. AC joint injuries are rare in throwingathletes except American football quarterbacks,although they can create major functional deficits as aresult of the disruption of the important AC linkage.Dyskinesis is found in a high percentage of patientswith high-grade AC symptoms.19 AC separationslessen and high-grade AC separations remove thestrut function of the clavicle on the scapula. Loss ofthe strut function permits the ‘third translation’ of thescapula, allowing it to move inferior and medial to theclavicle, changing the biomechanical screw axis of sca-pulohumeral rhythm, allowing excessive scapular inter-nal rotation and protraction and decreased dynamicacromial elevation when the arm is elevated.Iatrogenic AC joint injury as a result of excessivedistal clavicle resection and detachment of the AC liga-ments shortens the bony strut and allows excessivescapular internal rotation as a result of excessive anter-ior/posterior motion at the AC joint. The protractedscapular position creates many of the dysfunctionalproblems associated with chronic AC separations,including impingement and decreased demonstratedrotator cuff strength. However, scapular and shoulderdysfunction can also occur in type II injuries if the ACligaments are torn. This creates an anterior/posteriorAC joint laxity and can be associated with symptomsof pain, clicking, decreased arm elevation anddecreased shoulder function.

If dyskinesis is demonstrated on the clinical examin-ation, then increased attention should be directedtoward correcting the biomechanical abnormalityrather than just placing the arm in a sling. Treatmentshould include not only CC ligament reconstruction,

Ed Roche et al. 293

but also AC ligament reconstruction to completelyrestore the screw axis mechanism.

Clavicle fractures. Clavicle fractures may produce dyskin-esis if the anatomy is not completely restored. The dys-kinesis can be associated with alterations in shoulderfunction such as decreased strength and decreased armmotion in elevation.20 Shortened malunions or non-unions decrease the length of the strut, and alter thescapular position towards internal rotation and anter-ior tilt. In addition to changes in length, changes inclavicle curvature or rotation will affect scapular pos-ition or motion. Angulated fractures result in func-tional shortening and loss of rotation. The distalfragment in midshaft fractures often internally rotates,decreasing the obligatory clavicle posterior rotationand scapular posterior tilt during arm elevation.Dyskinesis can be a clinical sign of potentially harmfulalteration of clavicle anatomy, and can provide infor-mation to clarify indications for operative treatment inthese fractures.

Clinical examination of the scapula

Evaluation of the scapula should be carried out as aroutine component of the shoulder examination. Todetect scapular dyskinesis, clinical observation is usedto determine whether winging of the inferior or medialborders of the scapula is present. Assessment for scapu-lar prominence because of lift off from the thoracic wallis carried out in addition to detection of the lack of asmooth coordinated movement of the scapula duringforward flexion, shrugging or arm lowering from a pos-ition of full flexion. The motion can then be character-ized as dyskinesis as a ‘yes’ (presence of deviation ordysrhythmia/asymmetry bilaterally or ‘no’ (no pres-ence). This scoring system has proven interobserverreliability and clinical utility.21,22

A number of clinical tests have been devised thatemploy dynamic corrective manoeuvres to assess theeffect of correction of dyskinesis on shoulder symp-toms. The scapular assistance test (SAT) and scapularretraction test (SRT) help evaluate the degree to whichscapular dyskinesis, when corrected, may alter thepatient’s symptoms. The SAT evaluates scapular con-tributions to impingement and rotator cuff strengthwhereas the SRT can be used for evaluation in casesof labral symptoms and rotator cuff strength.

To correctly carry out the SAT, assistance for scapu-lar elevation is provided by manually stabilizing thescapula and rotating the inferior border of the scapulaas the arm moves (Figure 4). This procedure simulatesthe force-couple activity of the serratus anterior andlower trapezius muscles.23 If symptoms of impingementare diminished or eliminated by this manoeuvre, then

rehabilitation of the scapular stabilizing muscles islikely to help alleviate these symptoms.

The SRT involves manually stabilizing the scapula ina retracted position on the thorax. This position confersa stable base of origin for the rotator cuff and often willimprove tested rotator cuff strength. This test fre-quently demonstrates scapular and glenoid involvementin impingement lesions (Figures 5 and 6).23

Quantitative assessment of scapular stabilizerstrength can be achieved by the lateral scapular slide

Figure 5. Scapula retraction test: the examiner stabilizes the

medial border of the scapula as the arm is elevated. Relief of

impingement symptoms is a positive test.

Figure 4. Scapula assistance test: the scapula is stabilized with

one hand and the other hand ‘assists’ the scapula through its

correct motion plane.

294 Ed Shoulder & Elbow 7(4)

test (Figure 7).6 This test is semi-dynamic and evaluatesthree different positions of the scapula on injured andnon-injured sides in relation to a fixed point on thespine as varying amounts of loads are put on the sup-porting musculature. These positions offer a gradedchallenge to the functioning of the shoulder musclesto stabilize the scapula. The first position is with thearms by the side. The inferomedial angle of the scapula

is palpated and marked on both the injured and non-injured sides. The measurements from a fixed referencepoint are recorded. The second position is with thehands on the hips, the fingers anterior and the thumbposterior with approximately 10� of shoulder extension.The new position of the inferomedial border of thescapula is marked, and the reference point on thespine is maintained. The distances are calculated on

Figure 7. Lateral scapula slide test. (a) Initial position with arm at side. (b) Second position, arms on hips. (c) Third position with

arms at 90� and internal rotation.

Figure 6. Scapula retraction test with resistance. (a) the examiner performs a traditional ‘empty can’ test. (b) The examiner

stabilizes the medial border of the scapula and repeats the test. If the impingement symptoms are relieved, the test is positive.

Ed Roche et al. 295

both sides. A similar process is carried out for the thirdposition. The arms are held at or below 90� of forwardelevation with maximal internal rotation at the gleno-humeral joint. The threshold of abnormality is 1.5 cmand significant asymmetry is most commonly measuredin the third position.

An essential part of scapula examination is evalu-ation of the shoulder pathology or injury that couldbe causative of or exacerbated by the concurrent pres-ence of scapula dyskinesis. Rotator cuff integrity, labralstability and internal impingement should be soughtbecause they may represent the underlying cause ofthe dyskinesis.

Investigation and treatment of scapular dyskinesis

Investigations should be directed toward confirming anunderlying diagnosis. Nerve conduction studies may beof value if a specific traumatic precipitant causes injuryto the long thoracic nerve, dorsal scapular nerve orspinal accessory nerve. Electromyography studies canhelp identify injury and the potential for recovery inperiscapular muscles. X-rays can help identify clavicleor AC joint injury. Magnetic resonance imaging canhelp delineate muscle injury, whereas MR arthrogramscan identify associated labral pathology.

The mainstay of treatment for the scapulardyskinesis is physical therapy to relieve the symptomsassociated with inflexibility or trigger points and tore-establish muscle strength and activation patterns.6,23

Dyskinesis can often be caused by muscle inhibitioncreated by soft tissue related pathology such as labralinjury, internal impingement or rotator cuff pathologyor hard tissue injury such as clavicle fractures and ACseparations. In these instances, the surgical problemshould be addressed prior to commencing physical ther-apy to correct the dyskinesis.

Rehabilitation for scapular dyskinesis should startproximally and end distally. The ultimate goal of phys-ical therapy is to achieve the position of optimal scapu-lar function (i.e. posterior tilt, external rotation andupward elevation). Core stability exercises can helpimprove 3D control of scapular motion and this isachieved through an integrated rehabilitation regimenin which the larger muscles of the lower extremity andtrunk are utilized during the treatment of the scapulaand shoulder. Scapular protraction and retraction arefacilitated by hip and trunk flexion and extensionexercises.

Once core stability has been established, a focus onthe scapular controlling muscles can be initiated. Theserratus anterior muscle acts as a powerful externalrotator of the scapula, whereas the lower trapeziusacts as a stabilizer of the acquired scapular position.Re-education of these muscles to act as dynamic

stabilizers of the scapula is achieved by employingshort lever, kinetic chain assisted exercises and finallylong lever movements.2 This process may take at least6 months and appropriate patient counselling to ensurerealistic expectations is essential in the management ofthese cases. After achievement of adequate scapularcontrol and retraction, other issues such as rotatorcuff strength optimization or internal impingementcan then be addressed. The sequence of rehabilitationexercises may need to be adapted for individual casesbased on the rate of progress at each specific stage.

Future directions

Although scapular dyskinesis is a proven clinical entitythat can be responsible for shoulder pathology in manycases, there are still a number of unanswered questionsthat require further clarification. Dyskinesis seen inassociation with rotator cuff tears was identified as afactor related to lower functional scores.25 It remainsunclear whether scapular dyskinesis is a cause, effect orcompensation for rotator cuff pathology.

Summary

Scapular dyskinesis is a relatively new concept in theassessment of shoulder pathology. It is likely to be amajor contributor to shoulder pain, particularly incases of recalcitrant shoulder pain and dysfunction.Increasing evidence shows that the condition is emi-nently treatable in the majority of cases and canimprove with physiotherapy rehabilitation. It is advis-able that this condition is recognized as a constituent ofthe routine shoulder examination for shouldersurgeons.

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest withrespect to the research, authorship, and/or publication of thisarticle.

Funding

The author(s) received no financial support for the research,authorship, and/or publication of this article.

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