Adhesive capsulitis, commonly known as frozen shoulder, is a condition that causes extreme pain and stiffness in the shoulder joint. This pain can be due to a number of factors, including a decrease in the production of the synovial fluid that lubricates the joint, and thickening of the joint capsule that surrounds the shoulder joint. The decreased range of motion associated with frozen shoulder also causes pain, as the shoulder is unable to move as freely as it did before. Treatment for this condition includes physical therapy, anti-inflammatory medications, and in some cases, corticosteroid injections.