Possible causes of inability to straighten the little finger include trauma, joint dislocation, stenosing tenosynovitis and so on. 1. Trauma: there is a clear history of trauma, under the action of violence, the bone of the little finger is fractured, and after the displacement of the fracture end, the anatomical structure of metacarpophalangeal joint is changed, which leads to the influence of finger activity and can not be bent; or the extensor tendon of the little finger is ruptured due to trauma, and the little finger can not be stretched out without the driving force of the tendon. 2. Joint dislocation: because of falling, strenuous exercise, etc., the little finger is dislocated after excessive pulling, the joint loses its normal function, and the finger can not be straightened. 3. Stenosing tenosynovitis: because of overuse of the fingers, long-term chronic strain, trauma, etc., the tendon sheath of the little finger part of the aseptic inflammation, inflammation continues to stimulate the surrounding tissues, there can be finger pain, stiffness, difficulty in movement, popping and ringing and other symptoms. There are many reasons why the little finger is not straight, and it may be related to nerve injury, adhesion of periarticular tissues, palmar tendon contracture, etc. If the symptoms continue to be unrelieved, it is recommended to consult a doctor in time to clarify the cause of the disease and carry out targeted treatment.