i) Preoperative planning. A: femoral head center; AB: Fujisawa line; C: ankle center; D: Pivot point. Tibial shaft tracing distal to DC1 rotated laterally until point C lying on line AB, DC1 intersected medial tibial cortex to form point B1. C1B1 was the size of posteromedial bone graft. ii) Postoperative radiograph. Line AC intersected the knee joint at 30% lateral to knee center.