Frozen shoulder, also known as adhesive capsulitis, is a poorly understood condition which results in such decreased range of motion that the joint appears to be frozen in place. According to the American Academy of Orthopaedic Surgeons, frozen shoulder affects about 2 percent of the general population, most commonly people between the ages of 40 and 60, with no clear predisposition based on sex, arm dominance or occupation.
Immobilization
The causes of frozen shoulder are not completely understood, but some risk factors have been identified. According to the Mayo Clinic, shoulders that are immobilized in a sling after injury or surgery are more likely to experience frozen shoulder. Even shoulders that are simply protected from performing painful daily tasks are at risk for developing frozen shoulder. The shoulder joint is encased in a joint capsule, which can become thickened, tight and overrun with scar tissue if the shoulder is held in one position for prolonged periods of time. It is important to initiate early range-of-motion exercises whenever a shoulder must be immobilized in a sling.
Diabetes
According to the American Diabetes Association, frozen shoulder affects about 20 percent of diabetics, compared with 5 percent of non-diabetics. The exact mechanism for this correlation is still under investigation by the medical community. One theory reported by the American Diabetes Association involves the relationship of glucose molecules contributing to excess collagen deposits, resulting in loss of motion in the shoulder.
Other Possible Causes
There are many theories about possible causes of or risk factors contributing to frozen shoulder that are still not fully understood. According the American Academy of Orthopaedic Surgeons, frozen shoulder occurs more frequently in individuals who suffer from diabetes, hyperthyroidism, hypothyroidism, Parkinson's disease or cardiac disease. The American Diabetes Association reports that women are more likely to suffer from frozen shoulder, as are individuals between 40 and 60 years old. Frozen shoulder may be preceded by a shoulder injury such as tendinitis or bursitis, but this is not always the case.
