There are several possible causes of arm pain at night: first, myofasciitis, patients with myofasciitis often have pain on the inner side of the scapula as the first symptom, which can radiate to the ipsilateral shoulder and upper limb, resulting in soreness and weakness of the shoulder and upper limb, especially at night when sleeping under pressure, when the arm pain is very obvious, it is necessary to carry out relevant physical examination and examination to exclude other diseases for diagnosis; second, shoulder When the shoulder joint has frozen shoulder or rotator cuff tear, the arm pain can also be serious at night when sleeping. X-rays, CT and MRI of the cervical spine are performed for diagnosis and treatment.