Fig. 3

Measurement of different alignment parameters on hip-to-ankle anterior–posterior (AP) standing (a) and lateral (b) X-rays. Hip–knee–ankle angle (HKA) is the angle between the tibial mechanical axis and femoral mechanical axis, mechanical proximal tibial angle (mPTA) is the angle between the tangent of the medial and lateral tibial plateau and the mechanical axis of the tibia, and mechanical lateral distal femoral angle (mLDFA) is the angle between the tangent of the medial and lateral femoral condyle and the mechanical axis of the femur. Posterior tibial slope (PTS) is the angle between the tibial anatomical axis (a straight line connecting the midpoint of the line at 5 cm and 15 cm from the knee joint line) and tibial plateau (a line connecting the anterior and posterior points of the most proximal part of the tibial plateau)