Nighttime arm pain can be caused by physiological factors such as improper posture and pathological factors such as muscle strain, fasciitis, cervical spondylosis, lateral epicondylitis of the humerus, and medial epicondylitis of the humerus. 1. Physiological factors: for example, when you sleep at night, you feel the wind and cold, causing muscle spasm or sleeping in a poor posture, the arm is compressed. 2. Muscle strain: If you often do tired work, it can cause chronic strain of the arm muscles. 3. Fasciitis: trauma or strain caused by aseptic inflammation of the myofascia, local pain, stiffness, limited activity. 4. Cervical spondylosis: osteophytes or herniated nucleus pulposus compresses the nerves and causes radiating pain in the arm. 5. Epicondylitis of the humerus: If it occurs below the elbow joint, consider epicondylitis of the humerus, and the pain is aggravated by flexion and extension of the arm. 6. Epicondylitis of the humerus: Chronic pulling at the end point of the flexor muscles on the inside of the elbow joint causes aseptic inflammation, which involves pain on the inside of the arm. If the arm pain at night is not alleviated by rest, it is recommended to go to the hospital for examination to clarify the cause of the disease.