My doctor diagnosed my tight shoulder as "adhesive capsulitis." What is this, and how did it happen?

Adhesive capsulitis, also called "frozen shoulder," is a condition in which the shoulder becomes tight and painful, making it difficult to do daily activities.

With frozen shoulder, inflammation in the joint causes the lining surrounding the joint to stick together. This causes the shoulder to "freeze" and seriously limits movement.

It's hard to say how you got a frozen shoulder. Most cases can't be traced to one event. One theory is that this condition is caused by an auto-immune reaction. An auto-immune reaction happens when the body's defense system, which normally protects it from infection, mistakenly begins to attack the tissues of the body.

A frozen shoulder may arise gradually, with no injury or warning. It sometimes happens to people who've had past shoulder problems, such as rotator cuff tendonitis or bursitis. Others are affected after surgeries unrelated to the shoulder--even after heart attacks. The condition likely results when pain or inflammation in the shoulder causes a person to start using the shoulder less, setting the stage for a frozen shoulder.