Conditioned pain modulation does not differ between people with lower-limb tendinopathy and non-tendinopathy controls: a systematic review with individual participant data meta-analysis.

Abstract

OBJECTIVE: To explore whether people with lower-limb tendinopathy have reduced relative conditioned pain modulation (CPM) when compared to non-tendinopathy controls. DESIGN: Systematic review with individual participant data (IPD) meta-analysis. LITERATURE SEARCH: Eight databases were searched until 29 August 2022. STUDY SELECTION CRITERIA: Cross-sectional studies comparing the magnitude of the CPM effect in people with lower-limb tendinopathy to non-tendinopathy controls in a case-control design. DATA SYNTHESIS: Included studies provided IPD, which was reported using descriptive statistics. Generalised estimating equations (GEE) 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. RESULTS: Five records were included, IPD were provided for four studies (n=219 with tendinopathy, n=226 controls). The principal GEE (model one) found no significant relative CPM effects for tendinopathy versus controls (B=-1.73, p=0.481). Sex (B=4.11, p=0.160), age (B=-0.20, p=0.109) and body mass index (B=0.28, p=0.442) did not influence relative CPM effect. The Achilles region had a reduced CPM effect (B=-22.01, p=0.009). In model two (adjusting for temperature), temperature (B=-2.86, p=0.035) and female sex (B=21.01, p=0.047) were associated with the size of the relative CPM effect. All studies were low-quality, and the certainty of the evidence was moderate. CONCLUSION: 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 (e.g., tendon loading exercises such as heavy slow resistance). Based on the 'moderate' certainty evidence, future studies are unlikely to substantially change these findings.