Capsulitis, or frozen shoulder, is an incredibly painful condition that can last for months or even years. The primary cause of capsulitis is the thickening, tightening, and shrinking of the shoulder capsule that surrounds the joint. This thickening and tightening causes the shoulder capsule to become so tight that it restricts movement and makes any movement excruciatingly painful. The shoulder capsule's inability to move properly can also cause extreme inflammation and irritation of the surrounding tendons, muscles, and ligaments, further increasing the pain. Treatment for capsulitis typically includes physiotherapy, anti-inflammatory medications, cortisone injections, and in extreme cases, surgery. With proper treatment, however, many individuals are able to find relief from the pain and regain full shoulder mobility.