At the age of 18, Yang was suffering from shoulder pain. Recently, Dr. Na Jian, deputy chief physician of the Department of Bone and Joint Surgery of our hospital, and Dr. Wang Tao, attending physician of the Department of Bone and Joint Surgery, successfully removed more than 40 “joint rats” from Xiao Yang’s shoulder joint using minimally invasive arthroscopic techniques, helping him to relieve his pain. Xiao Yang is 18 years old and had intermittent shoulder pain half a year ago, but he thought it was due to excessive exercise and didn’t pay much attention to it. In the recent month, the pain worsened, accompanied by swelling and restricted movement, so he came to our bone and joint surgery department. According to Dr. Najian, intra-articular free bodies are caused by trauma to the joint or some specific lesions that cause fragments of cartilage, bone and other tissues to fall off and accumulate in the joint or by synovial metaplasia in the joint, which is like a hen laying an egg that constantly creates free bodies. Because the free body can change its position in the joint cavity due to joint movement, it moves around the joint like a mouse, so the intra-articular free body is also called a joint rat. Common causes include exfoliative osteochondritis, synovial osteochondromatosis, osteoarthritis and osteochondral surface fracture and intra-articular hematoma or infection. The clinical manifestations are mainly joint pain, swelling, effusion, and repeated interlocking. The disease is mostly seen in the knee joint and less commonly in the shoulder and ankle joints. The treatment used to be conventional large incision to remove the joint, which is traumatic, slow to recover and unsightly. There is almost no damage, quick recovery, almost no scarring, and the effect is ideal. For those who do not receive timely treatment or have developed comorbidities, the treatment is less effective and the symptoms do not disappear completely, leading to wear and tear of the articular cartilage and the development of osteoarthritis for a long time, leaving more serious complications. Therefore, early diagnosis and timely treatment are extremely critical. According to Yang’s condition, Dr. Na Jian, deputy chief physician, performed an arthroscopic minimally invasive free body removal surgery + synovectomy to remove more than 40 “joint rats” from Yang’s shoulder joint, and also performed a chemosynovial synovectomy to block the mechanism of synovial production and prevent the joint from being damaged. The synovial mechanism of synovial production was blocked to prevent the joint rats from regenerating. After the surgery, Yang’s shoulder pain was greatly relieved and he was discharged from the hospital.