Left shoulder pain predicts the following conditions: 1. Pain caused during daytime activities, such as when lifting or posterior extension, predicts aseptic inflammation or strain of muscles and tendons; 2. Weakness of the left shoulder, requiring right hand support when lifting up, and a history of trauma to the patient, predicts rotator cuff muscle injury or tear, suggesting ultrasound or MRI; 3. Pain in the left shoulder at night, or even waking up in pain, needs to exclude ischemic disease of the heart. In addition, shoulder calcification or inflammation can also cause severe pain in the shoulder at night; 4. Cervical disc herniation compressing the nerve can lead to pain in the shoulder area.