Soreness in the left shoulder can be caused by overactivity, cervical spondylosis, frozen shoulder, and other causes. It can be treated through lifestyle changes, medication and physical therapy. 1. Over-activity: overloading the left shoulder and heavy physical labor can lead to over-activity of the left shoulder joint, which can cause local strain and thus lead to left shoulder pain. You should stop moving your left shoulder and use hot water bags to apply hot compresses on the sore spot to relieve the pain. 2. Cervical spondylosis: there are degenerative changes in the cervical intervertebral discs, due to the nucleus pulposus of the intervertebral discs prolapsed, stimulating the compression of the nerve root, thus leading to pain. The use of vasodilating drugs, such as flunarizine hydrochloride, and oral non-steroidal anti-inflammatory and analgesic drugs, such as ibuprofen, etc., can provide some relief. 3. Frozen shoulder: it is mostly due to chronic injury caused by long-term over-activity, poor posture and degenerative diseases. Due to the stimulation of inflammatory factors, it can also cause left shoulder pain and limitation of activities. Non-steroidal anti-inflammatory drugs, such as acetaminophen, can be used in the acute stage under medical supervision. Exercise rehabilitation can also be taken to move the shoulder joint and other relief. In addition, left shoulder pain can also be seen in other causes, it is recommended that patients go to the hospital in time to do the relevant examination, to clarify the cause of the disease, and then follow the doctor’s instructions for treatment.