Sudden pain in the shoulder in the middle of the night is commonly caused by the following reasons: First, cold shoulder. If the environment is cold and no attention is paid to keeping the shoulder warm, it is easy for the shoulder to get cold and cause acute inflammation of the bursa around the shoulder joint, and the patient will have severe, sudden shoulder pain with limited movement of the shoulder. Secondly, in the middle stage of periarthritis, due to the irritation of the adhesive band, shoulder pain can also appear suddenly at night, mostly accompanied by severe limitation of shoulder movement, and the patient’s age is usually around 50 years old. Third, subacromial impingement syndrome can be secondary to rotator cuff injury. These patients can also present with sudden pain at night when the affected shoulder joint is compressed, and the pain can be extremely intense or even unbearable, and MRI can show acromegaly and rotator cuff injury.