The prevalence of shoulder pain has been reported to be between 2.4% and 26%. Primary adhesive capsulitis is reported to affect 2% to 5.3% of the general population. The prevalence of secondary adhesive capsulitis related to diabetes mellitus and thyroid disease is reported to be between 4.3% and 38%.
The glenohumeral joint is a synovial joint containing a syno- vial membrane lining the interior joint capsule and encasing the long head of the biceps tendon into the biceps groove. The glenohumeral capsule, coracohumeral ligament, and gleno- humeral ligaments (superior, middle, and inferior) comprise the capsuloligamentous complex. This complex surrounds the glenohumeral joint inserting onto the humerus (superior to the lesser tuberosity and surgical and anatomic necks), from the coracoid and glenoid rim via the labrum and glenoid neck. The capsuloligamentous complex and rotator cuff tendons create an intimate static and dynamic constraining sleeve around the glenohumeral joint.
The rotator cuff interval forms a triangular-shaped tissue bridge between the anterior supraspinatus tendon edge and the upper subscapularis border. The rota- tor cuff interval is primarily composed of the superior glenohumeral ligament and the coracohumeral ligament.
Adhesive capsulitis is marked by the presence of multiregional synovitis, consistent with inflammation, yet focal vascularity and synovial angiogenesis (increased capillary growth) rather than synovitis are described by others. Accompanying angiogenesis, there is evidence of new nerve growth in the capsuloligamentous complex of patients with adhesive capsulitis, which may explain the heightened pain response. Regardless of the synovial pathology being angiogenesis or synovitis, significant pain can result at rest or with motion.
Significant capsuloligamentous complex fibrosis and contracture are consistently observed upon open or arthroscopic shoulder surgery and histologic examination. The entire capsuloligamentous complex can become fibrotic, but the rotator cuff interval and specifically the capsuloligamentous complex are predominantly involved. The rotator cuff interval is part of the anterosuperior complex, which functions as a superior hammock. With the arm at the side, the anterior limb restricts external rotation while the posterior limb restricts internal rotation. Coracohumeral ligament release in patients with adhesive capsulitis resulted in a dramatic increase in shoulder external rotation motion. Others have noted significant subacromial scarring, loss of the subscapular recess, inflammation of the long head of the biceps tendon and its synovial sheath and musculotendinous contracture.
Clinicians should assess for impairments in the capsuloligamentous complex and musculotendinous structures surrounding the shoulder complex when a patient presents with shoulder pain and mobility deficits (adhesive capsulitis). The loss of passive motion in multiple planes, particularly external rotation with the arm at the side and in varying degrees of shoulder abduction, is a significant finding that can be used to guide treatment planning.
Although the aetiology of adhesive capsulitis has not been identified, there are a number of associated factors. Recent evidence implicates elevated serum cytokine levels as causing or resulting in a sustained intense and protracted inflammatory/fibrotic response affecting the synovial lining and capsuloligamentous complex in patients with adhesive capsulitis. To date, the relationship between cytokines and the causative factor, whether it is insidious or related to minor trauma, is unknown.
Individuals with type 1 or 2 diabetes mellitus have a greater propensity of developing adhesive capsulitis. Patients with Dupuytren’s disease or type 1 diabetes mellitus for 10 or more years have a greater incidence of primary adhesive capsulitis.
Thyroid disease is a risk factor associated with adhesive capsulitis. Milgrom et al reported that 13.4% of patients with adhesive capsulitis had thyroid dysfunction. The majority of the patients with thyroid disease who developed adhesive capsulitis were women.
Age can be considered a risk factor because ad- hesive capsulitis more commonly occurs in individuals between 40 and 65 years of age, with the reported peak incidence occurring, on average, between 51 and 55. Females appear to be affected more commonly than males. Having adhesive capsulitis on 1 side places an individual at risk (5%-34%) for opposite-arm involvement in the future, and adhesive capsulitis can occur bilaterally simultaneously up to 14% of the time.
Other associated risk factors include prolonged immobilization, myocardial infarction, trauma and autoimmune disease.