Fig. 9From: The magnitude and temporal changes of response in the placebo arm of surgical randomized controlled trials: a systematic review and meta-analysisMeta-analysis of pain trials with comparable late follow-up visits. Pooled SMD estimates for three trials with pain intensity as the primary outcome and follow-up visits at 3, 6 and 12Â months, ordered by sample size within subgroup. NRS numerical rating scale, VAS visual analogue scale, WOMAC Western Ontario and McMaster Universities Osteoarthritis IndexBack to article page