Understanding the Biomechanics Involved in a Frozen Shoulder

Frozen shoulder, also called adhesive capsulitis, is a painful condition that results from a thickening and shrinking of the shoulder joint. Patients with this condition find it difficult to move their shoulder and arm.

Shoulder Anatomy

• The shoulder has three joints: the glenohumeral joint, the sternoclavicular joint and the acromioclavicular joint.

  The glenohumeral joint is a ball-and-socket joint, and it is the joint most closely associated with frozen shoulder.

Frozen Shoulder

• Frozen shoulder occurs when the shoulder joint capsule shrinks and thickens, causing the glenohumeral joint to gradually lose its range of motion, or seem to "freeze."

Causes of Frozen Shoulder

• There are several causes of frozen shoulder, and many have to do with the biomechanics of the body. They include rotator cuff tears, osteoarthritis and bone fractures.

Treatment of Frozen Shoulder

• Frozen shoulder can sometimes be treated with nonsteroidal anti-inflammatory drugs such as acetaminophen, or with injected corticosteroids. These treatments are both meant to reduce inflammation and decrease pain in the shoulder joint.

  Physical therapy is also recommended for patients with adhesive capsulitis. Moving the head of the humerus around in the joint can sometimes loosen a stiff shoulder.