Functional anatomy – the surface area of the humeral head is two to four times that of the glenoid. The diameter of the humeral head is nearly twice that of the glenoid when measured in the transverse plane. This lack of particular contact contributes to the inherent instability of the gleno-humeral joint. Stability of the joint is provided by the surrounding musculature, by the fibro-cartilaginous labrum which creates a more conforming surface to the glenoid and by the shoulder capsule. Adhesive Capsulitis has been classified into primary (idiopathic) and secondary types. Primary cases occur spontaneously. Secondary cases commonly develop in response to trauma to the upper extremity, upper extremity immobilisation, and abnormal shoulder mechanics.
While the definitive aetiology of this condition is unknown, adhesive capsulitis has been reported to have associations with other conditions, including cervical spine disease, diabetes mellitus, rheumatoid arthritis, infectious myocardial infarction and pulmonary cancer. It occurs between 40-60 years of age, females being more prevalent than males, and the left shoulder more than the right. The explanation of the reasons behind this condition relate to the pathological changes involving fibrosis and thickening of the gleno-humeral capsule.
The condition is painful but self limiting (it will resolve on its own whether or not any interventions or medications are used), with the average duration of symptoms being 2.5 years, with external rotation decreasing.
Adhesive capsulitis has been reported to have associations with other conditions, specifically cervical pain (25%), calcium deposits (10%), and diabetes (6%).