If the head of the little finger is bent and cannot be straightened, consider tenosynovitis, extensor tendon injury, osteoarthritis, etc. 1. Tenosynovitis: Thickening of the tendon sheath due to chronic strain injuries can compress the tendon, causing pain when the tendon rubs against the tendon sheath during joint activities, restricting activities and making popping sounds. Surgery can be performed to loosen the tendon sheath. 2. Extensor tendon injury: when the extensor tendon is injured or ruptured, the fingers can be bent but not straightened, surgery is needed to repair the injured tendon. 3. Osteoarthritis: joint hyperplasia, degeneration, narrowing of the joint space and other causes of limited joint movement, can only be bent and can not be straightened, usually can be cleaned joint surgery. If you can’t straighten your thumb, we suggest that you go to the hospital in time to clarify the cause of the problem, and then go to the hospital for targeted treatment.