75 patients had closed treatment for a primary unilateral acute patellar dislocation. All patients were studied clinically, radiographically and for isokinetic thigh muscle performance a median of 11 (6-24) years later. During the follow-up, 37 patients had experienced recurrent dislocations. The functional outcomes were similar in patients with or without recurrence. Radiographically unstable patellar morphology, spontaneous reduction of the dislocation and low volume of hemarthrosis predisposed to recurrence.