With the advent of an aging population, knee osteoarthritis is a common disease that causes knee pain and dysfunction in middle-aged and elderly people. For all kinds of severe knee osteoarthritis, knee replacement is an effective treatment after conservative treatment has failed. Traditional total knee replacement involves replacing the worn-out parts of the femoral condyles, medial and lateral tibial plateaus, and patellar surface of the knee joint with an artificial prosthesis to regain a pain-free, stable, and mobile knee joint. In the 1990s, a large number of knee replacements were performed with very reliable surgical results, but in many cases, it was found that the lesions were limited to the medial compartment of the knee, which is the main weight-bearing area of the knee, the medial femoral condyle and medial tibial plateau. For this reason, the Department of Orthopaedics of Ruijin Hospital and the Department of Orthopaedic Surgery of Ruijin Hospital worked together to replace the medial femoral condyle and medial tibial plateau. For this reason, the Department of Orthopaedic Surgery at Ruijin Hospital has actively exchanged ideas with foreign counterparts and introduced minimally invasive unicondylar replacement surgery technology. Compared with the traditional total knee joint, unicondylar knee replacement surgery mainly targets the diseased medial compartment of the knee joint. Through a 6-8cm medial knee incision, only the medial femoral condyle and medial tibial plateau are osteotomized and then replaced with a prosthesis, which preserves more bone volume of the knee joint and also preserves the anterior and posterior cruciate ligaments of the knee joint. Due to the minimal surgical trauma, the patient felt little pain after surgery and was able to obtain good knee motion and get out of bed and walk around the next day. At follow-up, it was found that unicondylar knee replacements resulted in faster recovery of knee function, greater joint mobility, gait closer to that of a normal knee, and greater patient satisfaction than total knee replacements. In 1/3 of our knee replacement cases, unicondylar knee replacement is more appropriate, i.e., the patient has mechanical pain confined to the medial knee, no lateral knee pain or patellofemoral pain, knee flexion deformity <15?, anterior cruciate ligament function is intact, imaging shows narrow medial knee space, normal lateral space, posterior tibial plateau The joint surface is intact and the stress position is correctable inversion deformity. Strict surgical indications and continuous improvement of surgical techniques ensure good surgical outcome of unicondylar knee replacement.