UNDERSTANDING TENDON PAIN MECHANISMS THROUGH A SYSTEMATIC REVIEW OF WIDESPREAD MANIFESTATIONS OF UNILATERAL TENDINOPATHY
Authors: Heales L J , Lim E C W , Hodges P W , Vicenzino B 
Published: May 2013

IntroductionTendinopathy is a clinical condition within or around the tendon that is thought to arise from high volume repetitive overuse, causing microtrauma.1 The local changes at the tissue have been well documented and include disorganisation of the collagen bundles, an increase in ground substance, and deformation of the tenocyte nuclei,2 leading to clinical signs and symptoms. To date there has been a concentrated focus on the local tendon pathology—however the potentially widespread systemic effects on the pain, motor, and sensory systems of which there is nascent information are poorly understood. The purpose of this systematic review was to investigate the prevalence of widespread changes in patients with unilateral tendinopathy.MethodsA thorough search strategy including three electronic databases (Medline—via Ovid, PubMed, and Scopus) and references list were searched to February 2012 for English language papers relating to widespread manifestations in unilateral tendinopathy when compared to healthy controls. Two independent investigators assessed the quality of the included papers using the Epidemiology Appraisal Instrument.3 Data relating to population and methodology as well as the mean and SD for the outcomes of pressure pain threshold (PPT), cold pain threshold (CPT), heat pain threshold (HPT), grip strength (GS), reaction time (RT) and speed of movement (SoM) were extracted. Point estimates of effect for pooled data were calculated by a meta-analysis of differences between non-affected sites in those with unilateral tendinopathy compared to control participants.ResultsOverall, 5420 studies were identified from the search strategy, with 248 extracted for a detailed analysis and a total of 25 included within the review. Of the 25 included studies, there were 3 animal studies, 18 lateral epicondylalgia (LE), 2 patella tendinopathy, 1 Achilles tendinopathy, and 1 rotator cuff tendinopathy. Only LE had multiple studies that could be subjected to meta-analyses, with six studying PPT, three HPT and CPT, and two RT and SoM. Comparing the non-affected side of unilateral tendinopathy with the non-dominant or left side in healthy controls, mean differences were significantly lower for PPT (−144.34 kPa; 95% CI CI −169.52 to −119.16, p<0.001), HPT (1.13°C; 95% CI −1.83 to −0.44, p=0.001), and SoM (−20.71 cm/s; 95% CI −27.47 to −13.95, p<0.001), whereas it was significantly higher for CPT (3.09°C; 95% CI 1.80 to 4.38, p<0.001) and RT (35.08 ms; 95% CI 28.49 to 41.67, p<0.001). GS was significantly reduced (−21.43 N; 95% CI; −29.70 to −13.16; p<0.001), however there was significant heterogeneity (p<0.001), requiring caution in interpreting this result.DiscussionThis systematic review and meta-analyses demonstrates widespread manifestations in unilateral tendinopathy, mainly from studies of LE and requiring evaluation for tendinopathy at other sites. These results are concordant with evidence of bilateral deficits in other unilateral musculoskeletal conditions (eg, carpal tunnel syndrome,4 unilateral wrist pain5). It is not possible to determine if these deficits preceded or were a consequence of the unilateral condition. In any event, the presence of widespread changes in measures of pain and sensorimotor function in human studies imply that there are abnormal central nervous system processing. We propose that further study of these widespread changes might lead to better outcomes through improved management strategies.