Which Portion of Physiotherapy Treatments' Effect Is Not Attributable to the Specific Effects in People With Musculoskeletal Pain? A Meta-Analysis of Randomized Placebo-Controlled Trials

OBJECTIVE: We aimed to quantify the proportion not attributable to the specific effects (PCE) of physical therapy interventions for musculoskeletal pain. DESIGN: Intervention systematic review with meta-analysis. LITERATURE SEARCH: We searched Ovid, MEDLINE, EMBASE, CINAHL, Scopus, PEDro, Cochrane Controlled Trials Registry, and SPORTDiscus databases from inception to April 2023. STUDY SELECTION CRITERIA: Randomized placebo-controlled trials evaluating the effect of physical therapy interventions on musculoskeletal pain. DATA SYNTHESIS: Risk of bias was evaluated using the Cochrane risk-of-bias tool for randomized trials (RoB 2). The proportion of physical therapy interventions effect that was not explained by the specific effect of the intervention was calculated, using the proportion not attributable to the specific effects (PCE) metric, and a quantitative summary of the data from the studies was conducted using the random-effects inverse-variance model (Hartung-Knapp-Sidik-Jonkman method). RESULTS: Sixty-eight studies were included in the systematic review (participants: n = 5238), and 54 placebo-controlled trials informed our meta-analysis (participants: n = 3793). Physical therapy interventions included soft tissue techniques, mobilization, manipulation, taping, exercise therapy, and dry needling. Placebo interventions included manual, nonmanual interventions, or both. The proportion not attributable to the specific effects of mobilization accounted for 88% of the immediate overall treatment effect for pain intensity (PCE = 0.88, 95% confidence interval [CI]: 0.57, 1.20). In exercise therapy, this proportion accounted for 46% of the overall treatment effect for pain intensity (PCE = 0.46, 95% CI: 0.41, 0.52). The PCE in manipulation excelled in short-term pain relief (PCE = 0.81, 95% CI: 0.62, 1.01) and in mobilization in long-term effects (PCE = 0.86, 95% CI: 0.76, 0.96). In taping, the PCE accounted for 64% of disability improvement (PCE = 0.64, 95% CI: 0.48, 0.80). CONCLUSION: The outcomes of physical therapy interventions for musculoskeletal pain were significantly influenced by factors not attributable to the specific effects of the interventions. Boosting these factors consciously to enhance therapeutic outcomes represents an ethical opportunity that could benefit patients.