OBJECTIVES: To empirically assess the clinical effects of physiotherapy on pain in adults.

DESIGN: Using meta-epidemiology, we report on the effects of a 'physiotherapy' intervention on self-reported pain in adults. For each trial, the group difference in the outcome 'pain intensity' was assessed as standardised mean differences (SMD) with 95% CIs. Stratified analyses were conducted according to patient population (International Classification of Diseases-10 classes), type of physiotherapy intervention, their interaction, as well as type of comparator group and risks of bias. The quality of the body of evidence was assessed based on GRADE methodology.

DATA SOURCES: Systematic searches were carried out in MEDLINE and PEDro from 1 January 2004-31 December 2013. 174 trials (224 comparisons) met the inclusion criteria for the meta-analysis.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Randomised trials using 'no intervention' or of a sham-controlled design were selected. Only articles written in English were eligible.

RESULTS: An overall moderate effect of physiotherapy on pain corresponding to 0.65 SD-units (95% CI 0.57 to 0.73) was found based on a moderate inconsistency (I(2)=51%). Stratified exploration showed that therapeutic exercise for musculoskeletal diseases tended to be more beneficial than multimodal interventions (difference 0.30 95% CI 0.03 to 0.57; p=0.03). Trials with a 'no intervention' comparator tended to have a higher overall effect size than trials with a sham comparator (difference 0.25; 95% CI 0.09 to 0.41; p=0.004). In general, our confidence in the estimates was low, mainly due to high risk of performance biases and between-study heterogeneity.

CONCLUSIONS: Physiotherapy reduces pain in adults, but standardisation of interventions and focus on trial research with low risks of bias and reproducible treatment modalities are needed.

TRIAL REGISTRATION NUMBER: CRD42014008754.