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Orthopaedics: Patella
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