Eight RCTs met the criteria for inclusion (eight assessing functional disability and five assessing pain) and involved a total of 743 patients. At post-treatment, yoga had a medium to large effect on functional disability (d=0.645) and pain (d=0.623). Despite a wide range of yoga styles and treatment durations, heterogeneity in post-treatment effect sizes was low. Follow-up effect sizes for functional disability and pain were smaller, but remained significant (d=0.397 and d=0.486, respectively); however, there was a moderate to high level of variability in these effect sizes.