1.Braking: Decreased movement of the shoulder joint, especially the upper limb leaning on the side of the body for a long time, is considered to be the most important trigger of frozen shoulder. Braking usually occurs after trauma or surgery. Not only can a fracture of the shoulder or upper arm, improper braking for too long after a traumatic injury can cause frozen shoulder, but sometimes even the application of a neck and wrist sling after a fracture of the forearm or wrist, or the immobilization of the chest cast reduces the movement of the shoulder joint and can also cause frozen shoulder. In addition, heart surgery, thoracic surgery, female mastectomy, and sometimes even hepatobiliary surgery can also cause frozen shoulder on the same side of the shoulder. This kind of frozen shoulder after surgery may be related to postoperative pain and reduced shoulder activity. 2. Intrinsic shoulder joint pathology: Degenerative diseases of the shoulder joint itself, especially local soft tissue degenerative changes, can cause frozen shoulder due to pain and restriction of shoulder joint movement. The most common degenerative soft tissue diseases that cause frozen shoulder are tendonitis and tenosynovitis, followed by impingement syndrome and subacromial damage. These diseases can lead to the development of frozen shoulder due to further pathologic changes such as damage, adhesions, and contractures of the musculature, rotator cuff, bursa, and joint capsule. In addition, injuries to the shoulder, sometimes even minor ones, are also likely to be the cause of frozen shoulder. 3. Neighborhood diseases: The common neighborhood diseases are cervical spine disorders. There are many studies that show that patients with cervical spine disorders are much more likely to develop frozen shoulder, and patients with frozen shoulder are often accompanied by a significant decrease in lateral flexion and rotation of the ipsilateral cervical spine. The cause of cervical spine disorders triggering periarthritis is not well understood, but it may be due to decreased shoulder movement due to pain or muscle spasm in the shoulder and arm after spinal nerve root irritation, or due to neurological dysfunction of cervical spine disorders, especially autonomic nerve involvement. Therefore, caution should be taken when differentially diagnosing or determining whether a cervical spine disorder is causing frozen shoulder. Other adjacent diseases include heart disease, pulmonary tuberculosis, subphrenic disease, etc. 4. Neurological disorders: There are many clinical observations that show a higher incidence of frozen shoulder in patients with neurological disorders such as hemiplegia and nerve palsy. This may be related to the decrease in muscle strength and movement, such as Parkinson’s disease, where the incidence of frozen shoulder is as high as 12 or 7%, the reason for the high incidence is obviously related to the decrease in movement. 5, endocrine system diseases: diabetes, hyperthyroidism or hypothyroidism and other endocrine system diseases are also closely related to frozen shoulder, especially in diabetic patients, the incidence of their combined frozen shoulder can reach 10% to 20%. Therefore, endocrine dysfunction may also be one of the triggering factors for frozen shoulder. 6, immune function changes: Although the immune mechanism of frozen shoulder is not well understood, it may be related to the degenerative changes in tendon tissue such as the supraspinatus tendon that induce autoimmune reactions. The susceptibility of the elderly to develop frozen shoulder and the treatment of frozen shoulder with adrenal glucocorticoid injections support the argument that it is immune-related. In general, after the age of 50 years, the supraspinatus tendon and other areas become significantly thinner and worn, and focal necrosis occurs in the vascular deprivation zone at the tendon stop, which is often repeatedly impacted with the subacromial peak during abduction. Therefore, it is very vulnerable to damage and inflammation. Localized non-bacterial inflammation can produce a foreign body type cellular immune response and gradually extend to other parts of the rotator cuff and joint capsule, causing diffuse capsulitis. In addition, some patients with periarthritis have a relatively high rate of HLA-B27, immunoglobulin A, C-reactive protein and immune complex levels, which may be related to the autoimmune reaction caused by fibrous degeneration after soft tissue injury around the shoulder joint. 7. Postural disorders: A significant number of patients with frozen shoulder occur in occupations with poor posture, such as manual work and sedentary work, and patients with excessive posterior thoracic protrusion (hunchback) are obviously susceptible to frozen shoulder. This may be due to long-term bad posture or postural disorders caused by the tilt of the scapula, the shoulder peak and humerus also due to abnormal stress and position changes, gradually formed rotator cuff injury, potentially leading to periarthritis. 8, psychological factors: depression, indifference and other psychological factors also have a certain relationship with the occurrence of frozen shoulder. A significant number of patients with frozen shoulder can have a history of emotional instability and psychological trauma. Or there are cases of depression due to long-term illness, socio-economic pressure and depression. They are more sensitive to pain, i.e. people with a lower pain threshold tend to suffer from frozen shoulder. The possible reason for this is that once shoulder pain and inflammation occurs, these people tend to be too sensitive to pain and have a harder time regaining motor function. Although the causes of frozen shoulder are diverse, these many causes collectively cause mild, nonspecific inflammatory changes in the soft tissues of the shoulder joint, suggesting that frozen shoulder may be caused by multiple factors. Therefore, the treatment and prevention of frozen shoulder should be differentiated according to the predisposing factors.