Sudden pain and weakness of the small arm may be physiological factors, but also may be acute injury, cervical spondylosis and other factors. 1. Physiological factors: heavy physical labor, and for a long time, excessive force, will lead to the small arm area of the hand soreness and weakness of the symptoms, should be reasonable rest, and local massage and hot compresses, may gradually return to normal. 2. Acute injury: when the arm suffers from acute injury or excessive pressure, it will lead to sudden pain and weakness of the arm, which may be accompanied by numbness, swelling and other symptoms, and in serious cases, it will lead to limb dysfunction. 3. Cervical spondylosis: may be related to degenerative changes and localized injury of the cervical spine, when the acute attack, the nerve innervating the upper limbs caused by compression, will cause sudden pain and weakness of the arm, can also be accompanied by neck and shoulder pain, numbness of the upper limbs and other symptoms. Sudden pain and weakness of the small arm, excluding physiological factors, it is recommended to go to the hospital in a timely manner, under the guidance of the doctor’s standardized treatment.