2. Methodological criteria list (van Tulder 1997/2003).

Internal validity A. Was the method of randomization adequate? B. Was the treatment allocation concealed? C. Were the groups similar at baseline regarding the most important prognostic indicators? D. Was the patient blinded to the intervention? E. Was the care provider blinded to the intervention? F. Was the outcome assessor blinded to the intervention? G. Were co‐interventions avoided or similar? H. Was compliance acceptable in all groups? I. Was the drop out rate described and acceptable? J. Was the timing of the outcome assessment in all groups similar? K. Did the analysis include an intention to treat analysis? Descriptive criteria (external validity) L. Were eligibility criteria for entry clearly mentioned? M. Were the index and control interventions explicitly described? N. Were adverse effects described? O. Was the timing follow up measurements (short term/long term) described? Statistical criteria P. Was the sample size for each group described? Q. Were point estimates and measures for variability presented for the primary outcome measures? * Criteria A‐K constitute the internal validity criteria recommended by van Tulder (2003). Criteria L‐Q are the remaining descriptive and statistical criteria from their earlier list van Tulder (1997)