Frozen shoulder refers to a condition where the shoulder undergoes a process of painful stiffening leading to substantial loss of shoulder function. The term adhesive capsulitis is also used to describe this condition. Primary adhesive capsulitis involves the spontaneous development of a stiff shoulder in the absence of an identifiable injury or surgery. This occurs in approximately 2% to 5% of the general population most notably in patients with diabetes or thyroid conditions and has a slight predilection for females. Primary adhesive capsulitis remains a poorly understood condition within the medical establishment and identifying a singular cause remains elusive.
The natural history of a course of primary adhesive capsulitis follows a typical three-phase pattern. The first, or inflammatory phase, is heralded by the onset of at times severe pain, limiting shoulder and arm function and affecting sleep. The second, or frozen phase, describes a period of maximum stiffness in the shoulder often making it difficult for patients to perform even simple tasks with the affected arm. Pain has generally moderated in the frozen phase and may only be felt when patients attempt to move their arms beyond their available range of motion. The final, or thawing phase, involves the gradual return of shoulder function and resolution of pain.
Beyond the pain and stiffness in the shoulder, two elements of adhesive capsulitis can be of particular frustration and consternation for patients. First, patients struggle with the idea that they can experience such pain and dysfunction in the shoulder without the presence of structural injury. Imaging tests including MRI often appear unremarkable, though high quality MRI scans can detect thickening of the capsular tissue in the shoulder consistent with adhesive capsulitis. Secondly, and perhaps more troubling is the prolonged duration of symptoms that is typical in an episode of adhesive capsulitis. The process of completing all three phases of the condition can take several months and in some cases more than one year. The vast majority of patients will enjoy complete resolution of symptoms, however, and surgical intervention is required in only the most severe and protracted cases.
A second variety of frozen shoulder, often termed secondary adhesive capsulitis, occurs following trauma or surgery where injury and healing have led to a stiffening of the shoulder. In most cases this too will resolve with patience and appropriate exercise and surgical intervention is the exception not the rule.