Acute dislocation of the patella. A correlative pathoanatomic study.

The objective of our study was to elucidate the characteristic pathoanatomy associated with patellar dislocation and report the preliminary results of early surgical repair. Twenty-three patients with documented patellar dislocation had standard radiographs and a magnetic resonance imaging scan. Intraarticular lesions were evaluated and treated arthroscopically followed by an open exploration of the medial aspect of the knee in 16 patients. Twelve patients were observed for a minimum of 2 years after surgical repair (average, 34 months). Eleven patients returned for a follow-up examination. Magnetic resonance imaging revealed effusion (100%), tears of the femoral insertion of the medial patellofemoral ligament (87%), increased signal in the vastus medialis muscle (78%), and lateral femoral condyle (87%) and medial patellar (30%) bone bruises. Arthroscopic examination revealed osteochondral lesions involving the patella and the lateral femoral condyle in 68% of cases. Open surgical exploration revealed tears of the medial patellofemoral ligament off the femur in 15 of 16 patients (94%). After medial patellofemoral ligament repair, none of the patients experienced recurrent dislocation. Overall 58% of the results were considered to be good or excellent and 42% were fair. Fifty-eight percent of the group returned to their previous sport with no or minor limitations.