Synovial osteochondromatosis is generally a benign lesion. Synovial osteochondromatosis is a rare arthropathy characterized by the formation of cartilaginous nodules in the synovium. These cartilaginous bodies may protrude into the joint cavity, or detach into the joint cavity and become free bodies, which may undergo calcification or ossification. The disease occurs in the joints of the knee, hip, elbow, and shoulder, and is generally a benign lesion. The main symptoms of synovial osteochondromatosis include joint swelling, joint effusion, localized pain, and mobility problems. Usually, the site of pain varies with each episode, and sometimes patients can feel free bodies in the superficial part of the knee joint. In the early stages, arthroscopic surgery can be performed to remove the synovial membrane and remove the free body from the joint. If the symptoms are more severe, joint replacement surgery can be performed. Usually, the disease can be cured with active treatment and the prognosis is generally better.