1. Braking: Decreased movement of the shoulder joint, especially with the upper extremity leaning against the body and hanging on the side for a long time, is considered the most important trigger of frozen shoulder. Braking usually occurs after trauma or surgery. Not only can a shoulder or upper arm fracture or prolonged inappropriate braking after a traumatic injury cause frozen shoulder, but sometimes even reduced movement of the shoulder joint due to the application of a neck and wrist sling after a forearm or wrist fracture, or immobilization in a chest cast 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. Frozen shoulder after this surgery may be related to postoperative pain and reduced shoulder activity. 2. Intrinsic shoulder joint lesions: Degenerative diseases of the shoulder joint itself, especially local soft tissue degenerative changes, can cause frozen shoulder due to painful restrictions on shoulder movement. The most common soft tissue degenerative diseases that lead to frozen shoulder are tendonitis and tenosynovitis, followed by impingement syndrome and subacromial damage. These diseases can lead to frozen shoulder due to further opening into damage, adhesions, contractures and other pathological changes in the musculoskeletal, rotator cuff, bursa and joint capsule. In addition, injuries to the shoulder, sometimes even minor ones, are very likely to be the cause of frozen shoulder. 3. Neighborhood diseases: The common neighborhood diseases are cervical spine disorders. There are quite a few studies showing 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. Therefore, caution should be exercised when making the differential diagnosis or determining whether a cervical spine disorder is responsible for frozen shoulder. Other adjacent diseases include heart disease, pulmonary tuberculosis, and subphrenic disease. 4. Neurological disorders: There are more 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 the incidence of frozen shoulder in patients with Parkinson’s disease is as high as 12.7%, 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%-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 seems that it may be related to the autoimmune reaction induced by degenerative changes in tendon tissues such as the supraspinatus tendon. Phenomena such as the predisposition of older adults to develop frozen shoulder and the treatment of frozen shoulder with adrenal glucocorticoid injections during the treatment of frozen shoulder support the argument for an immune link. In general, after the age of 50 years, the supraspinatus musculature and other areas become significantly thinner and worn, and focal necrosis occurs in the vascular supply-poor zone at the tendon stop, which is often repeatedly impinged with the subacromial crest during abduction. As a result, it is very susceptible to damage and inflammation. Local evidence of nonbacterial inflammation can produce a foreign body-type cellular immune response that gradually extends to other parts of the rotator cuff and the joint capsule, causing diffuse capsulitis. In addition, some patients with frozen shoulder have relatively high immune indicators such as HLA-B27 positivity of human leukocyte-associated antigen, 1gA, C-reactive protein and immune complex levels, all of which may be related to autoimmune reactions 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 manual work, sedentary occupations with good posture, and patients with excessive posterior thoracic spine protrusion (hunchback) are obviously prone to frozen shoulder. This may be due to long-term poor posture or postural disorders that cause the scapula to tilt, and the acromion and humerus to change position due to abnormal stress, gradually forming rotator cuff injury, potentially leading to frozen shoulder. 8, psychological factors: depression, apathy and emotional urban depression 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 trauma. Or they may have a depressed mood due to long-term illness and socioeconomic pressure trap. They are more sensitive to pain, i.e. people with a lower pain threshold tend to be prone to frozen shoulder. The likely reason for this is that once shoulder pain and inflammation has occurred, these individuals tend to have a harder time regaining motor function because they are overly sensitive to pain. Although the triggers of frozen shoulder are diverse, these numerous triggers work together to cause mild, nonspecific inflammatory changes in the soft tissues of the shoulder joint, thus suggesting that the etiology of frozen shoulder may be multifactorial. Therefore, the treatment and prevention of frozen shoulder should be differentiated according to its predisposing factors.