The causes of cramp-like pain in the left arm while lying down to sleep include excessive compression, biceps tenosynovitis, and frozen shoulder. Treatment includes general treatment, physical therapy, drug treatment, surgical treatment and so on. 1. Excessive compression: If excessive compression is caused to the left arm when lying down to sleep, the above symptoms can also occur. It can be recovered by improving the posture and usually requires no treatment. 2. Biceps tenosynovitis: patients with mild symptoms can take oral anti-inflammatory and analgesic drugs such as diclofenac sodium extended-release tablets, etc., and in severe cases, local injection of glucocorticosteroids such as hydroprednisone, etc., can be combined with local massage, hot compresses and other physical therapy. 3. Frozen shoulder: Frozen shoulder can cause cramp-like pain in the left arm when lying down to sleep. The treatment includes functional exercise, local closure, medication such as ibuprofen extended-release capsules, acupuncture and physiotherapy, massage and so on. If the above treatments are not effective, soft tissue release surgery can be taken. In addition to the above causes, cervical spondylosis, epicondylitis of the humerus, ossifying myositis and other diseases can also cause the above symptoms. If the patient has the above symptoms, it is recommended to go to the hospital to find out the cause of the disease, and under the guidance of the doctor to carry out regular treatment. The above medications should be applied under the guidance of a pharmacist or doctor, avoiding self-medication.