I. Surgical incision The blood circulation around the skin incision of the knee is poor and prone to complications such as skin margin necrosis, so special care should be taken. 1. A median longitudinal incision of the knee can be chosen for the initial replacement. 2. The same incision should be chosen when there are scars from previous surgical incisions. 3. The outermost incision should be chosen when there are multiple scars from previous surgical incisions. The steps to be completed in the extended knee position are 1. Subcutaneous subcutaneous soft tissue dissection to the outer edge of the patella. 2, The medial edge of the patella is incised to access the knee joint. 3, Partial excision of the infrapatellar fat pad. 4, Partial excision of the suprapatellar bursa. 5, Subperiosteal dissection of the medial tibial condyles and lateral collateral ligaments. Generally, if the inversion deformity is less than 10° before surgery, the length of the peeled periosteum should not exceed 3 cm. 6.If the peripatellar osteochondral hyperplasia is severe and it is difficult to turn the patella, then an electric knife should be used to do peripatellar release and remove the osteochondral osteochondral. 7.Cut the patellofemoral ligament, flip or slide the patella, and flex the knee joint. 3. Steps to complete in the flexed knee position 1. extreme flexion of the knee joint and extreme external rotation of the tibial condyle. 2, Resection of the medial and lateral meniscus. 3, Bone cutter to remove the bony flab around the medial femoral condyle, medial tibial condyle and intercondylar fossa of the femur and remove the posterior cruciate ligament. 4.For patients with internal knee, resection of the medial tuberosity and subperiosteal debridement of the medial tibial condyle can basically achieve medial soft tissue balance. 5.Osteotomy of the tibial plateau is performed with the help of the tibial extramedullary positioning rod according to the osteotomy plane designed by the X-ray and the required posterior tilt angle of the prosthesis. The joint surface of the tibial plateau after osteotomy should have the same coronal surface and morphology as that designed on the preoperative X-ray. 6.Opening of the intercondylar fossa of the femur. The marrow opening point is mostly located between the highest point of the femoral intercondylar fossa and the lowest point of the femoral patellofemoral slide, with a little medial bias. It needs to be adjusted according to the position of the intersection of the longitudinal axis of the femur and the intercondylar fossa on the preoperative X-ray. The intramedullary femoral positioning rod is then inserted into the medullary cavity of the femur. If the intramedullary locator rod is inserted smoothly and completely, the point of entry is correct. A 5° valgus resection of the distal femoral articular surface is recommended. 7. When doing the anterior femoral condylar osteotomy, care should be taken to prevent its osteotomy surface from entering the anterior femoral stem bone cortex and causing fracture. The axis of rotation of the femoral prosthesis should be in line with the line of the medial and lateral epicondyles of the femur of the knee. 8. Clean the posterior soft tissues of the joint and remove any bone growth and free bodies from the posterior aspect of the joint. 9. Use the joint gap measurement block to measure the balance of the flexion and extension gaps in the 90° flexion and extension positions of the knee. The degree of medial and lateral opening should not exceed 2mm in the 90° flexion or extension position under internal and external rotation stress. 10. Femoral and tibial prostheses are repositioned in a trial mold. Observe: a) whether the axis of the lower limb in extension is satisfactory; b) whether the center point of the tibial plateau trial mold is consistent with the midpoint of the tibial plateau; c) whether the knee joint can be completely straightened; d) whether the patellar track is satisfactory; e) whether the medial collateral ligament is too tight by finger touch in the flexion degree position and extension position. 11. Complete the tibial plateau according to the instruments provided by the manufacturer, and mark the midpoint of the tibial plateau (inner 1/3 of the tibial tuberosity) before staking. IV. Release of the medial patellar support band If the patellar orbit is not satisfactory after trial mold repositioning, the release of the medial patellar support band should be done under the condition of testing while releasing, keeping the synovial layer intact as much as possible. V. Clean up the soft tissues below and above the patella to prevent extrusion and popping after surgery.