A unicondylar replacement is a special type of artificial knee replacement, one that is limited to the unicondyle.　　So what is unicondylar? Based on the shape and function of the knee joint, we divide the knee into two parts, the medial and the lateral. The medial one consists of the medial femoral condyle, the medial meniscus and the lateral tibial plateau. Similarly, the lateral portion consists of the lateral femoral condyle and lateral meniscus and the lateral tibial plateau. The medial and lateral condyles of the knee are different in shape and do not function in exactly the same way. Generally the medial condyle is under more pressure and the lateral condyle has more rotational function. Therefore, as people get older, decades of wear and tear often damage the cartilage of the medial condyle of the knee first, exposing the bone and eventually causing the typical osteoarthritis, which is when the bones rub against each other, causing pain and swelling in the joint and making it difficult to walk. Since only the medial condyle of the knee joint is worn out and the lateral condyle is still intact, only the aging wear of the medial condyle needs to be treated, resulting in unicondylar replacement surgery. There are many unicondylar artificial joints abroad. This joint retains the lateral condyle, patella, cruciate ligament and other structures, so the patient’s knee function is basically normal without the discomfort caused by total knee replacement. The trauma is small, the wound is only half that of a traditional total knee replacement, and the patient recovers quickly and at low cost. The picture on the left shows the surgery to install a unicondylar prosthesis with a small incision, about 8CM long. The right image shows the released articular surface of the medial tibial plateau, with severe wear of the anterolateral portion of the articular cartilage visible.