Thumb joint pain finger can not be straight, may be narrow tenosynovitis, thumb fracture dislocation, thumb osteoarthritis and other causes, should be timely consultation to find out the cause of the disease. 1. Stenosing tenosynovitis: it is a chronic aseptic inflammatory change of tendon sheath caused by mechanical friction, mainly due to the proliferation of connective tissue of tendon sheath, which causes the thumb not to be straightened, joint pain, and in serious cases, it can be accompanied by popping and finger extension obstacles, which leads to hand dysfunction and affects the patient’s daily work. 2. Thumb fracture and dislocation: If the thumb is squeezed by heavy objects, it may lead to thumb fracture, which can be manifested as pain and swelling of the thumb joint and the symptom that the finger cannot be straightened. If a fracture occurs, you need to go to the hospital to find out the cause. Usually, it can be treated by manipulation or surgery. 3. Osteoarthritis of the thumb: Commonly found in middle-aged and old people, it is related to cold, dampness, aging and degenerative factors. It is mostly caused by cartilage degeneration inducing aseptic inflammation, leading to the symptoms of swelling and pain in the thumb joint and inability to straighten the fingers. When the thumb joint pain can not be straightened there may be other reasons, the patient should consult the doctor in time to clarify the specific causes, and then targeted treatment.