The pain in the arm that always wakes up at night may be related to the following causes: 1. It may be due to excessive fatigue. This is often seen when the patient has done a lot of hand grasping, which in turn leads to muscle strain on the ventral and dorsal sides of the forearm, which produces a noticeable cramp-like pain here that may be accompanied by twitching of the hand. In addition, if the patient did excessive labor, resulting in tendon stop lesions, such as tennis elbow, golf elbow, and so on, may also produce severe pain during sleep at night, and then the patient woke up. 2, there may be peripheral nerve lesions. For example, if the patient has cervical radiculopathy or thoracic outlet syndrome, the patient may sleep on the side or other bad sleeping posture, resulting in nerve root compression, stimulation, and then produce very serious pain in the upper limb, so that the patient wakes up. 3, there may be caused by old injuries. For the upper limbs, there may be serious trauma, like fractures, dislocations and so on. If it is not properly treated in the early stage, or the injury itself is very serious, then it may leave severe pain after recovery, and there is an increase in pain during sleep at night.