Possible causes of pain at the joint between the small arm and the big arm include osteoarthritis, ligament or tendon injuries, bone fracture, and elbow canal syndrome. 1. Osteoarthritis: Osteoarthritis is often associated with inflammation, obesity, metabolic diseases and other factors, and when the joints are cold or strained, it can trigger pain and soreness in the joints. 2. Ligament and tendon injuries: Ligament injuries at the joints are usually caused by long-term weight-bearing and pulling, which makes the elbow joint unreasonably stressed and subjected to sudden violent attacks, etc. As the ligaments cannot withstand excessive tension, ligament injuries can occur, resulting in pain at the joints. It is also possible that tendon friction leads to epicondylitis of the humerus or epicondylitis of the humerus. 3. Fracture: If the patient has a traumatic injury such as an external object hitting the elbow, there may be a fracture of the elbow joint, which may cause severe pain and may be accompanied by symptoms such as limited mobility and local hematoma. 4. Elbow Canal Syndrome: Possible causes of elbow canal syndrome include subluxation of the ulnar nerve due to compression and abrasion, which in turn triggers elbow canal syndrome, and thus pain, numbness, and limitation of movement at the joint between the small arm and the big arm, i.e., the elbow joint, may occur. If you have pain at the joint between the small arm and the big arm, it is recommended that you go to a regular hospital in time to find out the cause of the pain and take active treatment.