Orthopaedics: Patella

Patellar Fracture

Mechanism

• a direct blow to the patella
• indirect trauma by sudden flexion of the knee against contracted quadriceps

Clinical Features

• marked tenderness
• inability to extend knee or straight leg raise
• proximal displacement of the 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 the patella after a 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 the 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 the patella

o       check for fracture of the 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 the 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 the patella
• commonly seen in active young females
• predisposing factors

o       malalignment causing patellar maltracking (patellofemoral syndrome)

o       post-trauma

o       deformity of the 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

• the sensation of instability, pseudo locking
• tenderness to palpation of the underside of the 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