Objective To assess the effect of medial distal femoral osteotomy combined with interlocking nailing on the treatment of knee osteoarthritis with valgus deformity. Methods From May 1996 toAugust 2000, 16 patients with knee osteoarthritis accompanied by valgus deformity were treated by medial wedged distal femoral osteotomy combined with interlocking nailing. Full-length radiographs were taken before operation and 8 weeks and 2 years after operation. The parameters, including the femorotibial angle, the tibial angle, the femoral angle, the femoral condyletibial plateau angle, and the lateral joint space, were measured by these radiographs. The function of knee was evaluated by the 100 point rating scale standard of knee. Results The mean postoperative score was significantly improved from 50.4±15.9 points to 78.5±12.9 points 2 years after the surgery. The lateraljoint space was increased from 2.1±1.8 mm to 4.7±1.7 mm and the femoral condyletibial angle decreased from 5.6±2.9° to 1.6±3.4°. There were complications in 2 cases: 1 case of delayed union and 1 case of superficial wound infection. Conclusion Medial distal femoral osteotomy combined with interlocking nailing proves to be an effective approach to treat knee osteoarthritis with valgus deformity.