Causes of Adhesive Capsulitis/Frozen Shoulder
There is no definite cause for adhesive capsulitis, however it's believed to be a result of inflammation and scar tissue developing in your shoulder capsule which shrinks your capsule size and limits shoulder and humerus movement. It generally starts as a little pinch of pain around the long head of your biceps tendon that doesn't get better. The shoulder capsule then starts to stick to itself and wraps tightly around your joint. The inflammation spreads and causes swelling in your other tissues like your bursa. The amount of synovial fluid (which helps the shoulder joint move) is decreased causing pain and lack of movement in your shoulder joint.
This condition can be a result of primary adhesive capsulitis or secondary adhesive capsulitis. Primary adhesive capsulitis occurs for no apparent reason (idiopathic cause). Secondary adhesive capsulitis is generally a result of changes in the structures and tissues supporting your shoulder and/or diseases.
There are a number of things that can cause damage to your shoulder muscles and tissues such as repetitive use or overuse from work or sporting activities, acute injuries and aging. Over the years your muscles will start to lose their mass and strength, your tissues will lose their elasticity and degenerate, making you more susceptible to injury. Weakened muscles and/or tendons or injuries to your rotator cuff (tears, impingements), arm or shoulder fractures, arthritis, bursitis, tendinitis or surgery can instigate adhesive capsulitis. You are at increased risk of suffering from this condition if your shoulder or arm have been immobilized or splinted and you haven't moved the area in a while.
Adhesive capsulitis has also been linked to poor posture or slouching which shortens the ligaments around your shoulder joint.
Some medical professionals believe adhesive capsulitis is caused from an autoimmune reaction, where your body's defense system attacks itself (it thinks its going after foreign material). This action causes inflammation in the tissues being attacked; as a result your shoulder freezes up.
Hormonal and genetic conditions also can influence your chance of experiencing adhesive capsulitis. People who suffer from diabetes, cardiovascular disease, heart disease, lung disease, chronic bronchitis, hyperthyroidism, hypothyroidism, Parkinson's disease, Dupuytren's contracture, or those who undergo breast surgery, heart attack or stroke (who are paralyzed on one side) where they are unable to move their shoulders through full range of motion for a period of time are at a higher risk as well.
Adhesive capsulitis is 5 times more common in people with diabetes, affecting 10 - 20% of people who have it. Glucose molecules attach to collagen (connective and/or scar tissue) in people with diabetes, which builds up in the joint and can cause the shoulder to stiffen.
Generally adhesive capsulitis occurs in people between 40 - 70 years of age; it is very rare in young people. 60% of women over 40 years of age have a risk of suffering from adhesive capsulitis, possibly as a result of hormonal changes during menopause. However it can occur in both men and women.