One of four normal people had mechanical alignment of 3 degrees varus and more than so-called “constitutional varus”. Parallel joint line to the floor found in both neutral and varus alignment. Therefore, joint line orientation may play an important role in clinical outcomes after TKA. For reconstituting joint line parallel to the floor advocated by 30 varus tibial cut that was introduced by Hungerford The prospective study conducted on 94 primary varus osteoarthritis knees undergone CAS TKA using either classical method (51 knees) or anatomical method (43 knees). Clinical outcomes including WOMAC scores, Oxford knee scores and ROM were evaluated preoperatively and 6 months postoperatively. Full leg standing hip-knee-ankle were measured mechanical axis, tibial cut angle and tibial joint line angle at 6 months after surgery. The results revealed that postoperative neutral alignment (mechanical axis 0± 3°), 4–5°varus and ≥6°varus showed no significant difference in term of WOMAC scores, Oxford scores and ROM. Including comparison between classical tibial cut and anatomical tibial cut, postoperative joint line parallel to the floor and oblique joint line had no significant in clinical outcomes. Nevertheless, anatomical tibial cut and joint line parallel to the floor had significant WOMAC scores improvement than the others. In conclusion, the joint line parallel to the floor may be one of key successes after TKA more than postoperative limb alignment.
