Rotator cuff degeneration and lateral epicondylitis: a comparative histological study.

OBJECTIVES Rotator cuff tendinitis and lateral epicondylitis are common in clinical practice but the underlying pathology is poorly understood. The study examined both normal and biopsy tendon specimens histologically, to determine the mechanisms involved in tendon degeneration. METHODS Rotator cuff tendons from 83 cadavers aged 11-94 and tendon biopsy specimens from 20 patients with lateral epicondylitis aged 27-56 years were examined histologically. RESULTS The microscopic changes found in the tendon biopsies from the elbow were similar to those found in the cadaveric rotator cuff tendons. Abnormalities ranged from minor blood vessel wall changes and loss of tenocytes to calcification. The most frequent abnormality was glycosaminoglycan infiltration and fibrocartilaginous transformation. There appeared to be some sequence in the changes observed which were milder in younger patients. Only 17% of cadaver tendons, below the age of 39 were abnormal but abnormalities increase in later life to around 40-50%. CONCLUSIONS There was an increasing incidence of degenerative changes in tendons with age. The changes observed in biopsy samples of common extensor tendons were the same as those seen in aged supraspinatus tendons, but these changes were not seen in control common extensor tendons.