Variants of the knee€¦ · (mucoid degeneration?) menisco-femoral ligaments Lee BY et al. Incidence and significance of demonstrating the meniscofemoral ligament on MRI. Br J Radiol

Variants of the knee

Franz Kainberger 1

Division of Neuro- and MSK Radiology & CIR Lab, Department of Radiology

Knee MRI: normal variants, incidential findings, and the borders to pathology

[email protected]

Your diagnosis, please

Alignment

Soft tissue

The clinically relevant variants of the anterior kneeMuscular balance and imbalance

The pediatric knee

Objectives: variants = normal structures < 50 %

jointbones Ossicles and sesamoids

Download PDF under: http://radiodiagnostik.meduniwien.ac.at/1/and on button Division of Neuroradiology and Musculoskeletal Radiology

Patellofemoral joint is visible on every MRI

Indications for imaging

Complex influencing factors, most importantlyfunctional (muscular) parameters

1. Bony dysplasias

• forms of patella: Wiberg „is out“

• Dysplasia of trochlea +/- lateral femoral condyle

• patella alta

• increased TTTG (tibial tuberosity-trochlear groove-distance)

• patellar tilt

2. Muskular imbalance

• Quadriceps

• Retinaculum insufficiency

3. Lower limb axis (valgus, valgus, anteversion)

femoropatellar malalignment

patellar subluxation with flattened trochlea

Trochlear dysplasia: in >90% of patellar dislocations

“quantitative measurements of the femoral trochlea have shown to be of limited value for the assessment of trochlear dysplasia“

trochlear inclination, trochlear facet asymmetry and depth of trochlear groove may help to distinguish between

• low-grade (Dejour A) and

• high-grade (Dejour C-D) dysplasia.

Nelitz et al. Evaluation of trochlear dysplasia using MRI: correlation between the classification system of Dejour and objective parameters of trochlear dysplasia. Knee Surg Sports Traumatol Arthrosc. 2012

Quantification of patellar malalignment

Dejour classification of trochler dysplasia.

M. Sinding-Larssen-Johannson

• Patellar tendinitis (jumper‘s knee)Repetitive extension of kneeduring landing phase of jump due to asymmetric quadriceps forces

• Many professional basket ball players show patella alta withoutany symptoms

Anterior knee overuse

Referral: suspected osteosarcoma

Patella alta and baja


Franz Kainberger 2

Hoffa‘s fat pad: anatomy

Hoffa‘s recesses: normal

Lig. transversum genus

fluid in proximal recess

superior Recess: 71 %inferior Recess: 45 %Aydingöz Ü et al. Eur Radiol 2004


Periostal gangon: may communicate with knee joint

Alignment

Soft tissue Muscular balance and imbalance

jointbones


Juvenile Baker‘s cyst: an own entity

• Fluid in 5 – 10 ys children• Spontaneous regression, surgery not

indicated• Diagnosis preferably with US

Medial gastrocnemius bursa

8 ys boy with popliteal swelling, especially when returning from school

Muscle variants: most are symptom free

• Third head of (lateral) gastrocnemius muscle

• M. popliteus bifurcatus:or accessory M. popliteusclinical relevance ? (ev. associated with ganglia)

• Quadriceps tendon:trilaminar layering of tendons is normal:DDx degenerative lipomatosis

• M. articularis genus

• Accessory biceps bellypotential compression of commmon peroneal nerve (Vieira et al., AJR 2007)

Muscle variants

M. popliteus bifurcatus. Tyler P et al., SkeletalRadiol 2010

Popliteal entrapment: 0.17 % of young males

12 variants described:

• asymptomatic or

• popliteal entrapment, if it crosses leg midlinebetween artery and vein

3rd head of M. gastrocnemius

Koplas MC et al. Skeletal Radiol. 2009;38:349

Muscular stabilizers of extensor apparatus

• Force from adductor and vastus medialis muscles:overactivity (soccer players)

„dimple sign“: atrophy and/or high insertion of vastus medialis muscle

• Hamstring shortening: increases pressure in patellofemoral jointleading to peripatellar tendinitis

• Vastus medialis oblique (VMO) muscle: primary stabilizer during knee extension

Superolateral patellar defect in lateral patellar compression syndrome.


Franz Kainberger 3

M. articularis genus

• stretches syovia of suprapatellar recess• atrophy and plica syndrome may be

associated

Puig S. et al., AJR 1996


Plica mediopatellaris type C: higherrisk of femoropatellar entrapment

Alignment

Soft tissueThe pediatric kneejoint

bones


MRI in children: routinely check for discoid meniscus

Discoid meniscus: forms• complete discoid meniscus

• incomplete form

• meniscal flounce: undulating contour of meniscus

• patchy inhomogeneities of lateral anterior horn

• Wrisberg-ligament type: hypermobile, often in children

Menisceal flounce (Tyler P et al. Skeletal Radiol 2009

Discoid is a meniscus, ifcontinuously visible on atleast three slices

Discoid meniscus: up to 5%

• up to 5 % of cases

• normal up to 11 mm, abnormal to 15 mm on coronar slices

complete type (Ahn JH et al. Am J Sports Med2009)

incomplete type

Discoid meniscus with complexrupture of anterior horn Wrisberg-type. Singh K

et al. AJR 2006;187:384

DDx to injury

• Menisco-menisceal andmenisco-femoral ligamentsmay imitate meniscal ruptures

• Cruciate ligament aplasia:rare, associated with congenital syndromesrotational istability is main clinical finding

Ligament variants

55-j. male with bucket-handle tear of meniscus

OMMLs: diagnostic criteria: display of whole ligament

Tyler P et al., Skeletal Radiol 2010

Sanders TG et al., Radiology 1999

• from anterior horn of one to posterior horn of othermeniscus

• from medial to lateral or from lateral to medial

• 2 – 4 % in humans, no mechanical function

• DDx: bucket-handle tears, displaced flaps, loosebodies

Oblique menisco-menisceal ligaments(OMMLs)


Franz Kainberger 4

double-PCL sign?

Humphrey ligament may imitate a double-PCL sign

pseudo-double PCL-sign, Tyler P et al., Skeletal Radiol 2010

• Humphrey ligament: small, ventrallytaut in flexion

• Wrisberg ligament: strong, dorsally,taut in extension

• variable insertion on medial femoralcondyle

• Reports about frequendy varying(to 83 % with MRI)less frequent with increasing age(mucoid degeneration?)

menisco-femoral ligaments

Lee BY et al. Incidence and significance of demonstrating the meniscofemoral ligamenton MRI. Br J Radiol 2000; 73; 271

the „third“ or anteromedial meniscofemoralligament

• Parallel to ACL, may be regarded as a separated anteromedial bundle

• very rare

• DDx: Lig. mucosum (infrapatellar plica): from distal patellar pole two fringes (alarfolds) convey to this ligament runnungthrough Hoffa‘s fat pad to anterior intercondylar fossa

Anteromedial meniskofemoral ligament. Tyler P et al., Skeletal Radiol 2010

Soejima T et al. Anteromedial meniscofemoralligament. Arthroscopy. 2003;19:90–5.

Infrapatellar plica. García-Valtuille, Radiographics 2002

ARRS Goldminer

ACL variants are rare

• Insertion into a discoid meniscus

• Hypoplasia, aplasia:with femoral hypoplasia, hemimelia orothers

often associated with variants of meniscior meniscofemoral ligaments

rotational istabilität is a possible finding

ACL: anterolateral (hypointense) und posteromedial (slighly hyperintense) bundle


Alignment

Soft tissuejoint

bones Ossicles and sesamoids:patella is the biggest sesamoid


Patellar variants may bedue to overload

• Patella partita and other patellar variants3 types: Type I : inferior pole of the patellaType II : lateral margin typeType III : supero-lateral type (most common)patella emarginata, patella tripartita

• Fabella, Cyamella

• Menisceal ossicles

Osseous variants

Patella partita overuse edema

superolateral patella defect may bedue to asymmetric muscle

Patella partita vs. patellar fracture

Sanders TG. Bone Contusion Patterns of the Knee at MR Imaging: Footprint of the Mechanism of Injury. Radiographics 2000


Franz Kainberger 5

Variants of patellar form

Wiberg types:

• Type I: medial and lateral facettes of same size (10%)

• Type II medial facette smaller (65%)

• Type III very small medial facett is steep and convex, lateral facette is large and concave (25%)flattened trochlea

Patella alta/baja

Patient with recurrent patellar luxations

Other sesamoids of the knee

Double patella

DDx chondroma of Hoffa’s fat pad

Fabella

• Sesamoid of lateral gastrocnemius

• may be degenerated

Cyamella

• Sesamoid of poplliteus muscle

• DDx Segond fracture

Fabella

Cyamella (Akansel G et al. Surg Radiol Anat 2006)

double patella

Normal and abnomallateral notch

Normal lateral condylopatellar sulcus

• 1 mm

Deep sulcus sign

• More than 2 mm deep

• associated findings of twisting injurywith tibial subluxation

Pao DG. The Lateral Femoral Notch Sign. Radiology 2001, 219: 800

Lateral femoral notch versus deep sulcus sign

Deep sulcus sign(M. Cobby et al. Radiology 1992)

normal notch

FMDs are no tumors, rather variants

Three forms or stages

• Cortical desmoid

• Fibrous cortical defect

• nonossifying fibroma

Probably resulting from increased musclestrenght during growth spurt.

Excluded from WHO bone tumorclassification

Fibrous metaphyseal defect (FMD)

FMD (radsource)

Posterior metaphyseal stripes

Laor T et al. Posterior Distal Femoral and Proximal Tibial Metaphyseal Stripes at MR Imaging in Children and Young Adults. Radiology 2002

• Reflect normal bonegrowth

Knee MRI: normal variants, incidential findings, andthe borders to pathology

Alignment

joints

Soft tissues

most deformities may be ratherdue to overuse than real variants

a wide world that may be conquered

Trochlea dysplasia (+ muscular imbalance) should be checked in every MRI

bones

thickened plicae and acessory ligaments


Documents

Variants of the knee€¦ · (mucoid degeneration?) menisco-femoral ligaments Lee BY et al. Incidence and significance of demonstrating the meniscofemoral ligament on MRI. Br J Radiol