Generally, thumb pain and inability to bend are considered as thumb fracture and dislocation, stenosing tenosynovitis, rupture of flexor tendon of thumb, etc. 1. Fracture and dislocation of the thumb: trauma, prolonged strain or prolonged compression by heavy objects can cause fracture and dislocation of the thumb, bone rubbing sound, bone rubbing sensation, abnormal movement of the fracture site, deformity and other signs, which can lead to the inability to bend the thumb and pain. 2. Stenosing tenosynovitis: it can occur in the thumb flexor tendon, also known as “trigger finger”, mostly seen in the hand labor crowd, the tendon sheath due to mechanical friction caused by chronic aseptic inflammatory changes caused by local pain in the thumb, can not be flexed, there can be stiffness in the morning, joints popping, etc., swelling and compression of the nerves can also cause numbness and other symptoms. 3. Rupture of the thumb flexor tendon: the thumb flexion action is controlled by the bunion long flexor muscle and bunion short flexor muscle, any one of the two muscle injury or tendon rupture can cause the thumb can not be bent. There are many other causes of thumb pain and inability to bend, such as rheumatoid arthritis, etc. It is recommended to consult a doctor for a clear diagnosis and targeted treatment under the guidance of the doctor.