Conditioned Pain Modulation Does Not Differ Between People With Lower-Limb Tendinopathy and Nontendinopathy Controls: A Systematic Review With Individual Participant Data Meta-analysis.

Abstract

<b>OBJECTIVE:</b> To explore whether people with lower-limb tendinopathy have reduced relative conditioned pain modulation (CPM) when compared to nontendinopathy controls. <b>DESIGN:</b> Systematic review with individual participant data (IPD) meta-analysis. <b>LITERATURE SEARCH:</b> Eight databases were searched until August 29, 2022. <b>STUDY SELECTION CRITERIA:</b> Cross-sectional studies comparing the magnitude of the CPM effect in people with lower-limb tendinopathy to nontendinopathy controls in a case-control design. <b>DATA SYNTHESIS:</b> Included studies provided IPD, which was reported using descriptive statistics. Generalized estimating equations (GEEs) determined between-group differences in the relative CPM effect, when adjusting for co-variables. Study quality was assessed using a Joanna Briggs Institute checklist, and certainty of the evidence was assessed using the Grading of Recommendations Assessment, Development, and Evaluations. <b>RESULTS:</b> Five records were included, IPD were provided for 4 studies (n = 219 with tendinopathy, n = 226 controls). The principal GEE (model 1) found no significant relative CPM effects for tendinopathy versus controls (B = -1.73, <i>P</i> = .481). Sex (B = 4.11, <i>P</i> = .160), age (B = -0.20, <i>P</i> = .109), and body mass index (B = 0.28, <i>P</i> = .442) did not influence relative CPM effect. The Achilles region had a reduced CPM effect (B = -22.01, <i>P</i> = .009). In model 2 (adjusting for temperature), temperature (B = -2.86, <i>P</i> = .035) and female sex (B = 21.01, <i>P</i> = .047) were associated with the size of the relative CPM effect. All studies were low-quality, and the certainty of the evidence was moderate. <b>CONCLUSION:</b> There were no between-group differences in the magnitude of the CPM effect, suggesting clinicians should manage lower-limb tendinopathy using interventions appropriate for peripherally dominant pain (eg, tendon loading exercises such as heavy slow resistance). Based on the "moderate"-certainty evidence, future studies are unlikely to substantially change these findings. <i>J Orthop Sports Phys Ther 2023;54(1):1-10. Epub 19 October 2023. doi:10.2519/jospt.2023.11940</i>.