Fig. 5

3-dimensional (3D) femorotibial angle (3DFTA) and the 3D hip-knee-ankle angle (3DHKA). The 3D anatomical and mechanical axes of the femur and tibia were defined in a 3D space and projected onto the coronal (xz) plane of the femur. The 3D mechanical axis of the femur was defined as the line connecting the center of the femoral head and the midpoint of the spheres representing the medial and lateral posterior femoral condyles. The 3D mechanical axis of the tibia was defined as the line connecting the midpoint between the medial and lateral eminences of the tibial spines with the center of the ankle joint