The number of total knee arthroplasty (TKA) performed in each year has been increased too rapidly, and the computer assisted orthopedic surgery (CAOS) using navigation in TKA is on the increase. However, the effectiveness of CAOS is still controversial and there are no evidence for the cost-effectiveness in Korea. In this study, we evaluated the short- and long-term effectiveness as well as cost-effectiveness of CAOS compared with conventional TKA.