Under normal physiological conditions, when the human body is in the standing position, the center of the femur and the center from the calf joint should be in the same straight line, and this straight line is the mechanical or mechanical axis of the lower limb. The average angle between the anatomical axis of the femur and the mechanical axis at the center of the knee joint via the femoral stem is about 6°; the tibiofemoral angle is the outward angle between the anatomical axis of the femur and the anatomical axis of the tibia at the center of the knee joint, and this angle is 174° on average. Proper knowledge and understanding of the significance of the anatomic axis of the femur lower limb mechanical axis and angle is essential to reconstruct a normal lower limb alignment during TKA surgery. In the pathologic situation, the normal tibiofemoral angle will be altered due to the inversion/eversion deformity of the knee and it will not be possible for the mechanical axis of the lower extremity to pass through the center of the knee joint. This is a critical issue that needs to be addressed by measurement and osteotomy in the preoperative planning and intraoperative management of the knee replacement. Elevation or reduction of the knee joint line will affect the relative position of the skeleton and the pulley, resulting in high or low skeleton. Therefore, reconstruction of the normal height of the joint line in TKA is also an important part of the procedure. On the other hand, although anatomically the tibial joint line has a certain amount of retroversion in the sagittal plane, the retroversion of the tibial articular surface is in fact almost zero, taking into account the meniscal factor. Therefore, it is not significant to emphasize the posterior tilt of the tibia of the knee prosthesis.