As our nation ages and the elderly population grows, so does the incidence of osteoarthritis of the knee joint, which is divided into three compartments: the medial compartment, the lateral compartment, and the patellofemoral compartment. Degenerative arthritis of the knee can affect any of these compartments, and 1/3 of patients with knee osteoarthritis have early lesions limited to only one compartment. In the past, knee replacements were mainly total knee replacements, but in our practice, we found that at least one third of these surgical cases only involved the medial compartment, the lateral compartment and patellofemoral compartment were good, and these good compartments had to be replaced in total knee replacements, which was very traumatic, with long postoperative recovery time and high surgical risk, which is a pity. The current surgical options for treating unicompartmental arthritis are unicondylar replacement, tibial high osteotomy, and total knee replacement. The tibial high osteotomy is mainly used as a transitional treatment to total knee replacement, which has the disadvantage of incomplete symptom relief and short duration of treatment, and is less used in older age groups. In contrast, unicondylar arthroplasty has received increasing attention due to improvements in prosthesis design, case selection, and surgical technique. Unicondylar arthroplasty is a minimally invasive surgical procedure that replaces the diseased articular cartilage and meniscus with an artificial unicondylar knee, while preserving the normal articular ligaments and other tissues. The mechanism of treatment is to use joint surface replacement technology to compensate for the loss of original tissue. In China, osteoarthritis of the knee joint in middle-aged and elderly people is most common in medial compartment arthritis, and the main pathological changes are: damage and exfoliation of articular cartilage, secondary synovitis, and formation of bone redundancy, causing joint pain, swelling, and dysfunction, which in severe cases leads to disability of the limb and affects the quality of life. With the rapid changes in science and technology, minimally invasive joint surgery has become a development trend, and is increasingly favored by patients because of its small incision, small surgical scope, reliable results, few complications, and fast functional recovery. However, not all patients with osteoarthritis are suitable for unicondylar joint replacement surgery, for example, rheumatoid arthritis is not suitable. His indications are mainly osteoarthritis of the medial compartment, inversion deformity and flexion contracture deformity are not heavy, the lateral compartment and patellofemoral compartment function is still good, there is a series of preoperative evaluation, if the evaluation can be implemented after unicondylar replacement, it is obvious that it can If a unicondylar replacement can be performed after the evaluation, it is obvious that pain relief and rapid recovery can be achieved. A unicondylar replacement is a small incision; a total knee replacement is a large incision and is very traumatic.