Evidence of Nervous System Sensitization in Commonly Presenting and Persistent Painful Tendinopathies: A Systematic Review

STUDY DESIGN: Systematic review. OBJECTIVES: To elucidate if there is sensitization of the nervous system in those with persistent rotator cuff (shoulder), lateral elbow, patellar, and Achilles tendinopathies. BACKGROUND: Tendinopathy can be difficult to treat, and persistent intractable pain and dysfunction are frequent. It is hypothesized that induction or maintenance of persistent pain in tendinopathy may be, at least in part, based on changes in the nervous system. METHODS: The PRISMA guidelines were followed. Relevant articles were identified through a computerized search in Embase, PubMed, and Web of Science, followed by a manual search of reference lists of retained articles. To be eligible, studies had to include quantitative sensory testing and evaluate individuals diagnosed with a-persistent tend inopathy of the rotator cuff (shoulder), lateral elbow, patella, or Achilles tendon. Methodological quality assessment was evaluated with the Newcastle-Ottawa Scale. RESULTS: In total, 16 full-text articles met the criteria for inclusion, of which the majority were case-control studies with heterogeneous methodological quality. No studies on Achilles tendinopathy were found. Mechanical algometry was the predominant quantitative sensory testing used. Lowered pressure pain threshold was observed across different tendinopathies at the site of tend inopathy, as well as at other sites, the latter being suggestive of central sensitization. CONCLUSION: Although more research on sensory abnormalities is warranted, it appears likely that there is an association between persistent tendon pain and sensitization of the nervous system. This evidence is primarily from studies of upper-limb tendinopathy, and caution should be exercised with inference to lower-limb tendinopathy.