The Long-Lasting Effects of "Placebo Injections" in Knee Osteoarthritis: A Meta-Analysis.

The placebo effect of knee injections is significant, with functional improvements lasting even longer than those reported for pain perception. The high, long-lasting, and heterogeneous effects on the scales commonly used in clinical trials further highlight that the impact of placebo should not be overlooked in the research on and management of knee osteoarthritis.