Total knee replacement with patellar dislocation is a relatively rare and challenging procedure, and only a few cases have been reported in China and abroad. Patients with severe knee osteoarthritis combined with patellar dislocation often present with the following anatomic abnormalities: 1) tibiofemoral joint valgus and external rotation; 2) medial soft tissue laxity and abnormal VMO development; 3) increased Q angle; 4) tension in the lateral support band; 5) patellar elevation, severe patellar deformity (concave), and patellar enlargement; 6) complex lower extremity torsion and femoral anteversion; 7) quadriceps shortening. The pathological and anatomical abnormalities of patellar dislocation determine the choice of surgical procedure. Patients often have multiple abnormalities, and the application of a particular surgical procedure alone may not be able to completely solve the problem, and multiple surgical methods must be combined to effectively stabilize the patella, and the most appropriate treatment should be selected according to the actual situation of the patient. Knee replacement provides an effective means of correcting tibiofemoral torsion and valgus deformity, and combined with knee extension device rearrangement can effectively correct patellofemoral dislocation and bring the knee extension device into play. Intraoperative operation points: 1, complete release of the lateral support band, moderate release of the lateral collateral ligament, posterior lateral joint capsule, iliotibial bundle, N tendon and other tissues; 2, removal of part of the patella, reduction of the patella, patellar prosthesis bias built-in; 3, tibial prosthesis moderate external rotation placed; 4, slightly increase the external rotation of the femoral prosthesis; 5, if necessary, the femoral osteotomy slightly increased to elevate the joint line (patella correspondingly decreased); 6, medial support band and The medial support band and the medial femoral muscle are overlapped and tightly sutured.