It has been reported that the maintenance of proper ligament balance around the knee joint and the proper location of tibio-femoral joint line position are very important factors for obtaining good knee joint function after the total knee replacement arthroplasty. but, yet the exact effect of the change of joint line on the result of total knee replacement arthroplasty has not been elucidated. The purpose of this study is to evaluate the effect of the change of joint line on the patellar position and the postoperative knee joint function as well as the effect of antero-posterior offset of tibial component on the clinical result. The authors performed the clinical and radiological analysis of 85 knees, in which total knee replacement arthroplasty was performed and followed over 1 year. Tibio-femoral joint line changed from -7mm to +6.8mm (average -0.07) and in this range, the change of joint line did not influence the clinical result and the patellar position. As tibio-femoral joint line migrated proximally, the patella migrated distally and as tibio-femoral joint line migrated distally, the patella migrated proximally. Postoperative pain decreased as the patella and patellar articular surface moved proximally. As the patellar bone height from tibial tuberosity decreased postoperatively. The range of motion decreased. Antero-ppsterior offset of tibial component distributed from -4.2mm to +4.5mm (average 0.62mm) and no effect on cllinical result in this range. In conclusion, it may be suggested that the change of joint line in total knee replacement arthroplasty must be changed as little as possible for the good postoperative range of motion and relief of pain.