Shoulder pain may be caused by physiological factors, frozen shoulder, periapical osteophytes, osteoporosis and so on. 1. Physiological factors: for example, prolonged heavy physical labor, resulting in an increase in local lactic acid metabolites, which will cause the symptoms of shoulder pain, and after reasonable rest, the symptoms of pain can generally disappear on their own. 2. Frozen shoulder: It mainly occurs in middle-aged and old-aged people, and the aseptic inflammation in the shoulder joint will cause shoulder pain and soreness, and when it is serious, it will also lead to the restriction of shoulder joint activities. 3. Periosteal hyperplasia: when there is hyperplasia in the shoulder joint, the hyperplasia may irritate the surrounding tissues, which will cause shoulder pain. 4. Shoulder muscle strain: prolonged exposure of the shoulder to cold and prolonged strenuous exercise leads to chronic strain of the shoulder muscles and aseptic inflammation within the muscles, which can cause double acid reflux pain. Double shoulder pain, the symptoms can not be relieved on their own, it is recommended to consult a doctor for examination and treatment in a timely manner to avoid delays in the condition.