Shoulder pain can be caused by a variety of diseases, of which “frozen shoulder” is the most well-known. “The concept of frozen shoulder was first mentioned in the late 19th century, when doctors believed that inflammation around the shoulder joint led to degeneration, adhesions and other changes in the tissues in the shoulder joint, resulting in pain and limited movement of the shoulder joint. However, due to the fact that the concept of “frozen shoulder” has been deeply rooted in people’s minds for a long period of time, some orthopedic surgeons who do not specialize in sports medicine are unable to correctly recognize the diagnosis of “frozen shoulder” and other related shoulder disorders, and many patients with shoulder pain have been misdiagnosed and their conditions have been delayed. Diseases Diseases related to shoulder pain 1. Frozen shoulder: A type of adhesive capsulitis that causes stiffness of the glenohumeral joint, a clinical syndrome mainly characterized by pain around the shoulder joint and limitation of movement in all directions. It mainly occurs in middle-aged and old people around 50 years old, and used to be collectively called “frozen shoulder”. 2. Acromioclavicular impingement sign: due to degenerative changes in the shoulder joint, the formation of subacromial osteophytes and bursa proliferation, the gap under the acromion becomes smaller, resulting in pain in the shoulder joint due to the extrusion of the rotator cuff and impingement when abducting or lifting up the arm. It can happen at any age, with middle-aged and old people being the most common. 3.Rotator cuff injury: it refers to the tear injury of rotator cuff tissue around the head of humerus, and the main cause is acromioclavicular impingement sign. Long-term rotator cuff impingement leads to rotator cuff degeneration, tendon quality decreases, and eventually injury tear. 4, biceps long head tendonitis: due to repeated physical labor caused by biceps long head tendon wear and tear and cause tendon tendon sheath congestion, edema and other inflammatory changes. It occurs in middle-aged people and mainly manifests as shoulder pain, but there is no limitation of activities in the direction of external rotation of the shoulder joint.