The elbow joint is one of the most important joints in the human body. It is involved in daily life such as eating, dressing, combing hair, reading and writing. 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 visualize and treat the elbow joint in all aspects through four small wounds of less than 1 cm. The most typical case is free body pressure resulting in incomplete extension of the elbow joint with pain. This can be restored to normal after arthroscopic treatment. However, the elbow joint is technically difficult due to the narrow joint space and abundant peripheral nerves, and there are fewer doctors in China who can do elbow arthroscopy well. Typical case: The patient was a 48-year-old male with pain and impaired mobility after a fall of the left elbow. Mobility: between 50-90°. X-ray showed coronal avulsion fracture, CT elbow degeneration and free body formation. After admission, we performed an arthroscopic exploration of the elbow and found a total of 4 free bodies formed in the coronoid process fracture, which were all removed.