Acute patellar dislocation is recommended for surgical treatment if the following conditions exist 1. After the patella is dislocated to the lateral side, during the reset, the medial inferior part of the patella impinges on the femoral epicondyle, which can result in a free body with a large osteochondral mass formed in the joint. The MRI and CT films showed a large osteochondral mass knocked off the medial aspect of the patella. The osteochondral mass was repositioned and fixed with absorbable nails to prevent localized osteochondral defects and osteoarthritis. The medial support band was tightly sutured during surgery to prevent recurrence of patellar dislocation. 2. There were obvious tears in the medial patellar support band and medial patellofemoral ligament. The MRI film showed a complete tear of the medial support band from the patellar rim, and the patient’s patella was dislocated laterally when the knee was passively flexed intraoperatively. The medially torn supporting band and ligamentous tissue were surgically sutured, which significantly maintained patellar stability and prevented recurrence of patellar dislocation.