Abstract
BACKGROUND: The pathophysiology of enthesopathy and tendinopathy is mucoid degeneration, which includes chondroid metaplasia. The chondroid metaplasia can be associated with calcification. Inflammation is typically absent unless calcification triggers a self-limited immune response representing acute calcific tendinitis. It is therefore important to address the hypothesis that calcific deposits within various entheses and tendons throughout the body are an inconsequential epiphenomenon of enthesopathy and tendinopathy and do not merit a distinct diagnosis or specific treatment. METHODS: We searched PubMed, Embase, and Web of Science for studies that address the prevalence of calcium in tendons and entheses with or without symptoms of tendinopathy, specifically excluding likely acute calcific tendinitis, and analyzed 35 studies meeting inclusion and exclusion criteria. Response variables included prevalence of calcification in and enthesis or tendon among people with no symptoms, among people seeking care for symptoms, and in the opposite asymptomatic limb, and the association between calcification and rotator cuff degeneration. RESULTS: Calcification of tendons and entheses was present on between 2.7 % and 8.6 % of radiographs of the shoulder, elbow, and ankle among people without symptoms and not seeking care, with higher percentages in older populations. Calcification was common among patients with symptoms: 44 % for rotator cuff tendinopathy, 25 % for enthesopathy of the origin of the extensor carpi radialis brevis, and 53 % for medial elbow enthesopathy. Most people with calcification had it bilaterally. Among people with calcification of the rotator cuff on MRI, nearly all of them (96 %) had tendon degeneration. CONCLUSIONS: The collective evidence regarding calcification in tendons and entheses suggests that it is related to mucoid degeneration and is not a separate disease process. Acute calcific tendinitis rapidly runs its course and is treated only to alleviate symptoms. It's not clear that acute calcific tendinitis or rotator cuff tendinopathy with calcification benefit from specific treatment of the calcium deposits. LEVEL OF EVIDENCE: Not applicable.