Orthopaedics: Patella

Patella

Patellar Fracture

Mechanism

·                 direct blow to the patella

·                 indirect trauma by sudden flexion of knee against contracted quadriceps

Clinical Features

·                 marked tenderness

·                 inability to extend knee or straight leg raise

·                 proximal displacement of patella

·                 patellar deformity

·                 ±effusion

Investigations

·                 x-rays: AP, lateral, skyline

·                 consider bipartite patelke congenitally unfused ossification centres with smooth margins on x-ray

Treatment

·                 non-displaced ( <2 mm)

o       straight leg immobilization 6-8 weeks

o       PT: quadriceps strengthening

·                 displaced: ORIF (>2 mm)

·                 comminuted: ORIF; may require partial/complete patellectomy

Patellar Dislocation

Mechanism

·                 lateral displacement of patella after contraction of quadriceps against a flexed knee

Risk Factors

·                 young, female

·                 obesity

·                 high-riding patella (patella alta)

·                 knock-knees (genu valgum)

·                 Q-angle (quadriceps angle) increased

·                 shallow intercondylar groove

·                 weak vastus medialis

·                 tight lateral retinaculum

Clinical Features

·                 knee catches or gives way with walking

·                 severe pain, tenderness anteromedially from rupture of capsule

·                 weak knee extension or inability to extend leg unless patella reduced

·                 +ve patellar apprehension test

o       patient apprehensive when examiner laterally displaces patella

·                 often recurrent, self-reducing

Investigations

·                 x-rays: AP, lateral, skyline view of patella

o       check for fracture of medial patella and lateral femoral condyle

Treatment

·                 non-operative first

o       knee immobilization x 4-6 weeks

o       progressive weight bearing and isometric quadriceps strengthening

·                 if recurrent

o       surgical tightening of medial capsule and release of lateral retinaculum, possible tibial tuberosity transfer, or proximal tibial osteotomy

Patellofemoral Syndrome (Chondromalacia Patellae)

Mechanism

·                 softening, erosion and fragmentation of articular cartilage, predominantly medial aspect of patella

·                 commonly seen in active young females

·                 predisposing factors

o       malalignment causing patellar maltracking (patellofemoral syndrome)

o       post-trauma

o       deformity of patella or femoral groove

o       recurrent patellar dislocation, ligamentous laxity

o       excessive knee strain (athletes)

Clinical Features

·                 deep, aching anterior knee pain

o       exacerbated by prolonged sitting (theatre sign), strenuous athletic activities, stair climbing, squatting

·                 sensation of instability, pseudolocking

·                 tenderness to palpation of underside of medially displaced patella

·                 pain with extension against resistance through terminal30-40°

·                 swelling rare, minimal if present

Investigations

·                 x-rays: AP, lateral, skyline

Treatment

·                 non-operative

o       continue non-impact activities

o       NSAIDs

o       PT: quadriceps strengthening

·                 surgical with refractory patients

o       tibial tubercle elevation

o       arthroscopic shaving/debridement

o       lateral release of retinaculum