What we should know about:

Patellofemoral disorders

AKRAM ALDAWOUDY, Mch.orth., FRCS

Patellofemoral disorders

• Anatomy• Biomechanics• Pathology• Common clinical entities

AnatomyThe patella

• Patella is the largest sesamoid bone• Thickest articular cartilage in the body

• Up to 5mm at central ridge• Articular surface is divided into the lateral

facet and the medial facet • Four different anatomical shapes probably

the result of the stress imposed on it.

AnatomyThe trochlea

• Asymmetric medial and lateral facets, with the lateral facet little more prominent and more proximal

• The greater height of the lateral facet of the trochlea and the congruence between the sulcus and the ridge are important for stability and constitutes a structural bony stabilizer.

AnatomyMedial Stabilizers

Medial retinaculum• Including medial patellofemoral ligament• MPFL runs from medial border of patella to

adductor tubercle• 75% restraining medial force • Vastus Medialis obliquus• Pulls at 55 to 70 degrees

Anatomy Lateral Stabilizers

• Lateral retinaculum• Superficial attaches to ITB• Deep, 3 bands

• Connects to IT band, tibia, & lateral epicondyle• IT band moves posteriorly in flexion

• Contributes to tilt and subluxation• Vastus lateralis

• Main muscle inserts proximally at angle of 31 deg• Vastus lateralis obliquus

• Distinct distal portion from lateral intermuscular septum

• The patalla pushes away the patellar tendon from the femorotibial contact point, increasing the patellar tendon moment arm (pulley action)

• Centralization of the divergent forces and transmit them in a frictionless way to the tibial tubercle

• Thichest articular cartilage, highiest compressive forces

Biomechanics

Biomechanics

• Joint reaction forces, the result of the tension developing in the quadriceps and patellar tendons (multiples of body weight)

• 0.5 level walking• 3.3 stair climbing• 7.8 squats

• Patellofemoral contact areas, moves proximally and broadens with increasing flexion.

• Patellofemoral contact pressure, ratio of patellofemoral reaction ferce to patellofemoral contact areas, most important

• Patellofemoral contact pressure increases with patellar malpositioning, as patellofemoral contact areas decrease

Biomechanics

Angle of pull of the quadriceps (Q-angle)

Line drawn from ASIS to Mid-patella and Line drawn from mid-patella to tibial tubercleNormal Q angle= 15

Pathology

• Traumatic: bony chondral ligamentous Merchant’s classification, sophisticated, though comprehensive

• Atraumatic, Insall classification

Insall Classification

• Presence of cartilage damage chondromalacia Osteoarthritis osteochondritis dissicans• Variable cartilage damage

malalignement syndromes synovial plicae• Usually, normal cartilage

peripatellar causes: bursitis, tendinitis Overuse syndromes Reflex sympathetic dystrophy Patellar abnormalities

Pathology

• Primary OA

• Pat fem maltraching

Chondral Pathology

• Diagnosis• history: pain on getting to stairs and

on kneeling, clicking, age, trauma• Clin. exam: patellar squeeze,

tender undersurface, tend lat.retinaculum

• Imaging: plain probably enough, MRI ?!!!

ALWAYS LOOK FOR AN

UNDERLYING FACTOR

Chondral Pathology

• Treatment: still a problem, especially in young pts. Depends on:• Age of the pt., age of the knee• Generalized or localized lesions• Underlying factor, Maltraching• Stage of the disease

Chondral Pathology

• Conservative management should be always tried first

RestReduction of wt.Restriction of activitiesQuadriceps trainingNSAIDSPT

Chondral Pathology

• Treatment:• Operative, DECECION CATIOUSLY TAKEN• Correction of the underlying

maltraching• Lateral retinacular release, may lead

to worse results ??!! • Articular cartilage management, from

cell to metal

Chondral Pathology

• Arthroscopic debridement/chondroplasty• Microfracture• Chondral grafts• ACI

• Generally less successful than for condylar lesions

• Anterior Displacing Osteotomies• Fulkerson

• angled for less medialization• Maquet

• avoid huge grafts

Chondral Pathology

• Patellectomy Mainly of historical interest• Patellofemoral arthroplasty Generally for older, lower demand patients Not as well proven as TKA• TKA Gold standard if coexistent femoral-tibial arthritis Reasonable in older, low demand patients with severe PF and some other compartment disease

Maltraching

A- Acute dislocation:• Usually presents to A&E after an injury!! Easy

reduction• Often hemarthrosis

• If aspiration returns fat then suspect fracture• 40% risk of osteochondral injury

• Many missed on Xray• MRI better• Most often medial patellar facet and lateral

femur• Most often underlying alignment issues

Maltraching

• Treatment of acute form:• Extend knee to reduce• If x ray changes, fat in joint, or crepitus

consider scope• Physical therapy• Primary repair of MPFL only in selected pts.

• 50% will probably need eventual surgery• Early interveniton may increase chronic

pain and arthrofibrosis

Maltraching

B-The chronic form:• May present with pain and/or mechanical

symptoms• Medial and lateral patellar translationCompare medial to lateral and side to sideApprehension test

Careful planning

Maltraching

Consider:• Overall limb alignment, valgus knee, valgus heel,

femoral anteversion…• Trochlear geometry• Patellar tilt• Quadriceps function• Age, style of life …• Beware of hyperlaxity, bilaterality• Rotational alignment of the whole limb• Degree of sublaxation• Only dynamic instability !!!• Degree of articular cartilage pathology• J-sign, pat height

QQ

Maltraching

• Radiology• Good quality x rays• Whole leg standing films• Tangential views• CT• MRI ??!!!

Maltraching

Conservative treatment• Rest, Ice, NSAIDS• Physical therapy

• Should be tried for several months before more aggressive measures

• Avoid aggressive quad strengthening if pain important

• Patellar tracking braces• Avoidance of offending activities

Maltraching

Surgical treatment: tailored for every pt. indiviually• Lateral release: Probably to be done with

lateral patellar compression syndrome• Distal realignment: Transfer, anterior, anteromedial, posteromedial (not done) Osteotomies, valgus knees

Maltraching

• Proximal realignment: Trochleoplasty, Good results in well selected cases, open and recently !!! arthroscopic MPFL reconstruction “advancement”, commonly done now, different techniques, isolated gracilis graft or a strip of patellar tendon

Take home message

• Patellofemoral joint disorders one of the very complex issues

• Look at the limb as a whole• Conservative measures always come first• Surgery may be devastating if not carefully

planned for• Lateral release over done ??!!• MPFL reconstruction coming to be a

standard procedure

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