Sudden bending of the finger without straightening is commonly associated with tenosynovitis, also known as trigger finger, which is characterized by impaired straightening. Traumatic dislocation or fracture should also be excluded. 1. Trigger finger is stenosing tenosynovitis, which is mostly characterized by pain and unfavorable flexion and extension of the affected finger, mostly accompanied by trigger movements. In severe cases, the affected area will be swollen and painful, and the finger will remain in the flexed or straightened position, resulting in the inability to flex and extend, and interlocking phenomenon. 2. Dislocation or fracture caused by traumatic factors: If the patient has impaired movement after traumatic factors, fracture or dislocation needs to be excluded, usually accompanied by symptoms of swelling and pain. When the finger suddenly bends and can not straighten, you need to consult the hospital in time, under the guidance of the doctor for examination and treatment.