In daily life, the human shoulder joint is engaged in activities in all directions, including forward flexion, back extension, abduction, internal retraction, external rotation and internal rotation, plus the circular rotation movement of the shoulder joint. With the wear and tear, aging of the joint, strain on the tendons and ligaments, and cold stimulation or trauma to the shoulder, it is very easy to have shoulder pain. Clinically, there are many patients with shoulder pain, and most of them often ask the same question during the consultation: “Doctor, do I have frozen shoulder?” In fact, there are many causes of shoulder pain, so which diseases can cause shoulder pain? Here are a few common diseases that cause shoulder pain. 1.Frozen shoulder: Also known as frozen shoulder. It is easy to occur in people around fifty years old, more women than men, so it is also called “fifty shoulder”. According to Chinese medicine, it is mostly caused by the wind and cold in the shoulder, so it is also called “frozen shoulder”. It is a condition in which the soft tissues around the shoulder joint, such as tendons, tendon sheaths, bursa and joint capsule, restrict the movement of the shoulder joint, causing shoulder pain and impaired movement. 2. Biceps long head tendonitis: This is a condition in which the long head tendon of the biceps muscle is damaged at the humeral tuberosity groove, causing impaired shoulder joint movement. It is one of the common causes of shoulder pain, but the shoulder does not freeze, so care should be taken to differentiate it from frozen shoulder. 3.Supraspinatus tendonitis: The disease starts slowly, and it usually occurs in middle-aged and young people, often with a history of minor trauma and cold. The pain is mainly at the large nodes of the shoulder peak, and radiates to the neck and shoulder and upper limbs. 4.Subacromial bursitis: Mostly seen in men aged 30~40 years old, mostly due to excessive exercise, chronic strain or rheumatism, the main symptom is shoulder pain, especially when abduction and internal rotation are aggravated. The main symptom is shoulder pain, especially when abducting or internally rotating. The affected shoulder muscle stiffness and shoulder joint movement are limited, and when examined, there is often significant pressure pain on the lateral aspect of the shoulder peak. 5. Rotator cuff calcification: It refers to the deposition of calcium in the tendons of the rotator cuff, which causes shoulder pain and restriction of movement. In the acute stage, the onset of the disease is sudden and there is often a history of trauma or overexertion. The pressure and pain in the shoulder joint are severe, but usually the pain disappears in 1~2 weeks and the shoulder joint activity is gradually restored. 6.Suprascapular nerve impingement syndrome: It refers to the compression of the suprascapular nerve, which manifests as pain in the scapula and shoulder joint, mostly with a history of chronic or acute injury, weakened abduction and external rotation of the shoulder joint, atrophy of the supraspinatus and infraspinatus muscles, and positive upper arm cross test, which is easily misdiagnosed as frozen shoulder. 7. Tumor: Severe shoulder pain, especially at night, no relief, rapid progress and poor prognosis. The prognosis is poor, such as osteosarcoma and fibrosarcoma. Some benign lesions, such as poor bone fiber structure, bone cyst, synovial chondromatosis, etc., can cause shoulder pain. If you have the above mentioned conditions, you should take a film in time to clarify the diagnosis as soon as possible and treat it actively. 8. Systemic diseases: such as rheumatoid arthritis, polymyositis, rheumatism, etc. Certain metabolic diseases such as gout and osteoporosis can also cause shoulder pain. 9. Visceral diseases: Certain visceral diseases can also cause involved shoulder pain, such as cholecystitis, right subdiaphragmatic abscess, hepatitis, heart disease, pneumonia, etc., when the shoulder examination is negative. In conclusion, there are many causes of shoulder pain. If the pain does not improve after conservative treatment and worsens day by day, you should go to the hospital for a comprehensive examination in order to avoid delaying the disease and to prevent it early and treat it early.