Orthopaedics: Patella

2021-02-19 12:00 AM

Patella fracture, mechanism, treatment and risk factors

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