Fig. 5

a HKA, formed by the mechanical axis of the femur (connecting the center of the femoral head and the center of the knee, blue line) and the mechanical axis of the tibia (connecting the center of the ankle and the center of the knee, red line). HKA, hip–knee–ankle angle. b MPTA, formed by the tibial mechanical axis (connecting the center of the ankle and the center of the knee, red line) and the line tangential to the proximal tibial articular surface (blue line). MPTA, medial proximal tibial angle. c TB, determined as the angle between the proximal third (yellow line) and distal third (blue line) mid-shaft axis. TB, tibial bowing