Mosley et al. (2002) conducted a randomized, placebo-controlled trial to evaluate the efficacy of arthroscopy for osteoarthritis of the knee. Patients were assigned to receive an arthroscopic debridement, arthroscopic lavage or placebo surgery. Patients and assessors of outcome were blinded to which condition the patients were in. Outcomes were assessed at multiple points over a 24-month period. Five self-reported scores and one objective test of walking and stair climbing was used as measures. Neither of the intervention groups reported less pain or better function than the group receiving the sham surgery. In fact, at two weeks participants that received the sham surgery performed better on an objective walking and stair climbing measure than those in the debridement group. This was also found at one year and the debridement group showed a trend towards worse functioning at two years. However, it is not clear if this outcome occurred due to a placebo (via expectation) effect or natural history.
Placebo Effects- Sham Knee Surgery (video)
Coming Soon! The Amazing World of Placebo Effects