Measurement of preoperative mechanical axis angle (MAA), mechanical femoral angle (MFA), and mechanical tibial angle (MTA) on a standing anteroposterior radiograph of whole lower extremity. The hip center, femoral notch center, and ankle center were also assigned and connected, and the angle between these lines was defined as MAA of the knee. The MTA was defined as the medial angle between the mechanical axis of the tibia and a line tangential to the tibial plateau. The MFA was defined as the medial angle between the mechanical axis of the femur and a line tangential to the distal femoral condyle.