The elbow joint is one of the very important joints in the human body. It is involved in daily life such as eating, dressing, combing hair, reading, writing and so on. However, the elbow joint is very prone to stiffness, flexion and extension disorders, which seriously affects daily life and reduces the quality of life. With the advancement of arthroscopic technology, it is now possible to observe and treat all aspects of the elbow joint through four small wounds of less than 1cm. The most typical case is that the elbow joint cannot be fully straightened with pain due to free body pressure. It can be normalized after arthroscopic treatment. However, the elbow joint has a narrow joint space and abundant peripheral nerves, so the technical difficulty is very high, and there are fewer doctors in China who can do elbow arthroscopy well. Typical case: the patient is a 48-year-old male with pain and impaired mobility of the left elbow after a fall. Mobility: between 50-90°. X-ray showed coronal avulsion fracture, CT elbow joint degeneration and free body formation. After admission, we performed arthroscopic exploration of his elbow and found a total of 4 free body formations in the coronoid process fracture, which were all removed, and postoperative mobility was good up to 0-140°.