Fig. 2

The schematic images of patient position when taking radiographs. A AP view: ensuring the lower leg was in a neutral position (the patella was orientated precisely to the center of the femoral condyles, and the feet should point forward at the same time) when the bottom edge of the foot ring was flat on the examining table or parallel to the horizontal line. B and C Lateral view: rotating the lower leg and ensuring the lateral edge of the foot ring are flat on the examining table or parallel to the horizontal line. D Two rulers were used to ensure the edge of the foot ring was parallel to the horizontal line when the edge could not flat on the examining table