Fig. 2.

Proportion of trials with (a) indistinguishable placebo, (b) inert placebo, (c) structurally equivalent placebo, (d) naïve subjects, (e) blinding assessment, (f) successful blinding (successful = both assessed and found to be successful; unsuccessful = not assessed or assessed and found to be unsuccessful). Assessments of patients’ expectations were also considered under blinding assessment. Graphs report group of interventions investigated in ten or more trials. Acupuncture (n = 10), electrotherapy (n = 20), exercise (n = 10), SMT (n = 12), pharmaceutical (n = 65). SMT spinal manipulative therapy