Condition analysis: There may be cervical spondylosis or scapulohumeral periarthritis. If there is only pain in the left arm and shoulder, the latter is more likely. Suggestion: Do an MRI of the neck and an X-ray of the shoulder to provide a differential diagnosis. If scapulohumeral periarthritis is caused, it will heal itself by reducing labor and functional exercise. You can also use some local drugs, such as painkillers.