Surgery should be performed as early as possible to reconstruct the knee extension device. With early treatment, the knee joint function is mostly restored and the accompanying deformity can be gradually corrected with growth and development. The incision is made from the middle and lower thigh along the iliotibial bundle to the tibial tuberosity. The node is curved medially, and the contracture tissue on the lateral side of the patella is fully loosened, including the lateral side of the patellar ligament, and the distal end of the lateral femoral muscle is cut off longitudinally from the junction of the iliotibial fascia, the lateral edge of the quadriceps tendon, and the lateral edge of the patella, and freed upward to be prepared for reconstruction. Cut off the contracture of iliotibial bundle, if the contracture of biceps femoris is obvious, then make extension, at this time, the contracture tissue of lateral patella has been completely loosened. 2.Reset of patella is cut along the inner edge of patella between rectus femoris muscle and medial femoris muscle, at this time, the patella can be reset to the intercondylar space of femur. If the quadriceps tendon and patellar ligament are still not straight, and there is still power of external patellar dislocation in the flexed knee, half of the lateral patellar ligament can be shifted and sutured to the medial side until the tibial tuberosity is shifted downward. 3.Repair and suture the soft tissues, strengthen the knee extension device by removing part of the medial lax joint capsule and synovial membrane, and then tighten the suture. After the medial femoral muscle is slightly upward free, the muscle belly tissue is used to cover the patella and sutured to the outer edge of the patella to strengthen the strength of fixing the patella in a neutral position. The distal end of the released vastus lateralis muscle is displaced upward and sutured to the upper part of the quadriceps tendon to reduce the force of pulling the patella outward. The medial excess joint capsule and synovium were resected to repair the lateral synovial defect. During the operation, the knee was flexed at 90°, and the patella no longer slid outward, which was considered satisfactory. Postoperatively, the long leg was immobilized with plaster cast for 6 weeks, and the contraction function of quadriceps muscle was exercised at an early stage, and the knee extension and flexion activities were practiced after removing the plaster cast.