Adhesive Capsulitis: What Is It?
Adhesive capsulitis is the currently accepted term for one of several disorders grouped under the umbrella heading "frozen shoulder." This group includes any combination of shoulder conditions that contribute to reduced range of motion (ROM) at the glenohumeral joint, including arthritis; bone spurs; bursitis; rotator-cuff tears; and impingement syndrome. These problems occasionally lead to secondary adhesive capsulitis, but require different types of intervention for complete resolution.
Adhesive capsulitis is an idiopathic (of unknown cause or origin) problem with a peculiar and unique presentation. It typically has a long, slow, painful onset ("freezing"), followed by a period during which pain is reduced, but function is severely restricted ("frozen"), and finally, a period during which all pain subsides and function is fully or nearly fully restored ("thawing"). The entire process can take anywhere from a few months to well over a year.
Adhesive capsulitis can afflict anyone at any age, but it is seen most frequently among women in their 50s. Some researchers suggest that it affects as much as 2 percent to 3 percent of the population at some point, and somewhere between 10 percent and 15 percent of those patients may have it bilaterally.
Because the shoulder joint has less supporting connective tissue than most joints in the body, it has unparalleled mobility and a huge normal range of motion. Even the capsular ligament that links the humeral head to the glenoid fossa is looser than most joint capsules. This increases mobility, but it leaves the shoulder vulnerable to a number of injuries other joints typically don't face, because they're better protected.
When the process of adhesive capsulitis starts, the joint capsule begins to adhere to the humeral head. Sometimes, this process is secondary to another injury that limits shoulder use, but it also can occur without any discernable trauma or trigger. This time frame, during which the adhesions between the humerus and the capsular ligament progress and worsen, is the first of three stages, sometimes referred to as the "freezing" stage. The first stage of frozen shoulder can last for two to four months, and is acutely painful in both active and passive movements of the shoulder. Typically, range of motion is lost in medial rotation first, but may progress to all directions.
The second or "frozen" stage of adhesive capsulitis lasts anywhere from four months to a year. During this time, the joint capsule thickens and essentially glues itself to the humeral head - particularly the anterior portion. Although range of motion is severely limited during this time, much of the pain usually subsides.
Perhaps the most mysterious thing about adhesive capsulitis is that after many months of severely limited movement in the shoulder, and progressive formation of connective tissue adhesions between the joint capsule and humeral head, the condition begins to resolve spontaneously. The joint capsule becomes free, pain is eradicated and movement is restored. This process may take a long time; a year or more is not unusual. If completely untreated, it is likely that range of motion at the shoulder joint may not be fully re-established, but the percentage of lost function (again, this is usually in internal rotation) is often not significant enough to warrant further interference. The goal of many treatment options is to ensure that when the adhesions begin to melt, the fullest possible range of motion is recovered.