Wrist pestle and mortar arm dare not bend back may be injury, tendonitis, rheumatoid arthritis, elbow tube syndrome and other causes. 1. Injury: if the patient’s upper limb is injured by external force, there is a serious fracture, dislocation, and then the arm does not dare to bend back. 2. Tendonitis: when the patient is affected by trauma, inflammatory diseases, repetitive motion leading to joint strain, etc., inflammation will occur in the tendon attached to the bone or muscle at the beginning of the expansion to the adjacent joints around the structure, the patient’s main manifestation of the affected parts of the pain, swelling, and impaired mobility, and the emergence of the phenomenon of the arm does not dare to bend back. 3. Rheumatoid arthritis: if affected by the environment, infection, genetics and other factors, the patient will not dare to bend the arm back, with the development of the disease, the patient will be swollen and painful, accompanied by fatigue, muscle aches and pains and other symptoms. 4. Elbow tube syndrome: when the nerve in the elbow through the ulnar nerve groove is compressed by the tendon membrane, abnormal muscles or bony changes, so that the patient will not dare to bend the arm back, mainly manifested as pain in the elbow area and so on. It is recommended that patients go to the regular hospital in time, under the diagnosis of the doctor, according to the specific performance of the patient’s condition, to take targeted treatment.