There are many factors that cause pain on the inside of the elbow at the bend back, such as elbow joint injury injury, humeral medial epicondylitis, rheumatoid arthritis and so on. 1. Elbow joint injury: long-term use of the elbow for gravity labor or strenuous exercise will lead to elbow joint strain, causing pain on the inside of the elbow bend back. 2. Epicondylitis of the humerus: Repeating a movement for a long time to play ball will lead to aseptic inflammation of the medial epicondyle of the humerus, which will make the local tissues edematous, oozing, and degenerating, thus causing swelling and pain on the inner side of the elbow at the elbow’s return bend. 3. Rheumatoid arthritis: if the elbow joint is infected with group A streptococcus or living in a damp and cold environment for a long time, it will lead to damage to the elbow joint and the surrounding tissues, which will lead to the phenomenon of pain on the inner side of the elbow return bend. 4. Trauma: If the elbow is pulled or hit by external forces, it will lead to local muscle ligament and other soft tissue damage, which will cause the elbow to bend back to the inner side of the pain. In order to relieve the pain on the inside of the elbow, it is recommended to go to the orthopedic department of the hospital in time to find out the cause of the disease and carry out standardized treatment.