Patient selection: A. Patients with severe pain B. Urgent request for surgery C. Ability to understand and insist on postoperative rehabilitation D. Ineffectiveness of previous treatments 2. Preoperative preparation: A. Reduction of risk factors for surgery for systemic diseases B. Soft tissue conditions C. Degree of bone defect D. Three-dimensional alignment of the affected knee E. Full-length films of the lower limbs 3. Preparation for surgery: A. Drawing of lines on the X-ray B. Preparation for the surgical bed and position C. Marking of useful reference points during the operation 4. C. Mark useful reference points during surgery 4. Surgical incision: A. Median approach B. If there is a previous surgical scar, choose the outermost scar as the approach C. Medial patellofemoral capsulotomy 5. Surgical field of view: A. Extensor mobilization tips from simple to complex. B. Resection of the bony residuals first. C. Soft tissue release: cut patellofemoral ligament, remove 1/3 of infrapatellar fat pad D. Stiff knee: release lateral support band to aid visualization E. If patellar ligament is in danger of tearing, pin a fixation nail to prevent tearing 6. Optimal osteotomy: A. Joint space is not displaced: femoral intramedullary, tibial extramedullary; B. Ankle center marking: 40% medial, 60% lateral C. Tibial osteotomy: After femoral osteotomy → soft tissue balancing → marking with gap module Tibial osteotomy: After femur is removed → soft tissue balance →Tibial osteotomy: <15mm below the highest point, <5° posterior tilt D. Three-dimensional alignment E. Selection of prosthesis size: note that the tibial and femoral prostheses do not go together F. Rotational positioning of the femoral prosthesis: mark the through-condylar line and Whiteside's line 7. Equalization of flexion-extension gaps: 5mm laxity → to avoid postoperative pain 8. Optimal cementing technique: 9. Optimal patellofemoral track: 10. Femoral joint orbit: Lateral patellar soft tissue laxity: 90°flip in the midline 10. Final balance and ROM after joint capsule suturing