Shoulder pain is a common complaint in the primary care setting. Prevalence studies indicate that 16 to 34 percent of the general population suffers from shoulder pain [1,2]. Patients with rotator cuff pathology comprise a sizeable portion of this subpopulation. A thorough understanding of the anatomy and pathophysiology of the shoulder will help the clinician evaluate these patients.
The clinical pathophysiology, diagnosis, and management of rotator cuff tendinopathy will be reviewed here. The general evaluation of the patient with shoulder pain, the shoulder examination, other specific shoulder problems, and general treatments for tendinopathy are discussed separately. (See "Evaluation of the patient with shoulder complaints" and "Physical examination of the shoulder" and "Overview of the management of overuse (chronic) tendinopathy" and "Presentation and diagnosis of rotator cuff tears".)
Knowledge of the pathogenesis of tendon overuse disorders remains incomplete. Histopathological, biochemical, and molecular studies reveal a degenerative process with little evidence of inflammation, although inflammation may play a role initially. The pathophysiology of chronic tendon disorders is discussed separately. (See "Overview of overuse (chronic) tendinopathy".)
The term "tendinitis" came into common parlance to describe chronic painful tendon injuries before the underlying pathology was better understood. The terms "tendinosis" or "tendinopathy" may better describe chronic tendon disorders. Despite support for the term "tendinopathy" among experts, the term "tendinitis" is deeply ingrained in clinical practice and the historical literature. In this review, we use the term "tendinopathy" to refer to symptomatic primary rotator cuff tendon disorders.
EPIDEMIOLOGY AND RISK FACTORS
The incidence of shoulder complaints is approximately 11.2 cases per 1000 patients per year . Shoulder pain occurs more often in the elderly [1,4]. In working populations, the incidence of shoulder-related symptoms may be as high as 14 to 18 percent . (See "Evaluation of the patient with shoulder complaints".)