The inability to straighten the arm is the limitation of the straightening function of the elbow joint, and the possibility of the disease suffered can be analyzed from several aspects: I. In terms of traumatic injury, there may be soft tissue trauma, including acute injuries, which can not be straightened because of the pain, and chronic strain injury caused by the soft tissue adhesion and can not be straightened. There may also be joint dislocation, intra-articular fracture or periarticular fracture, which is a sequela of inadequate functional exercise or poor repositioning. Secondly, in terms of degeneration, there may be osteoarthritis of the elbow joint, with osteophytes and narrowing of the joint space causing straightening dysfunction. Third, there may be long-term strain resulting in epicondylitis of the humerus or medial epicondylitis of the humerus, and localized pain can cause restriction of joint extension. Fourth, some hemiplegic cerebrovascular patients, because of motor function involvement or innervation problems caused by arm extension limitations.