Fake knee surgery relieved arthritis pain just as well as the real operation

In a 2002 trial, surgeons gave some osteoarthritis patients real arthroscopic knee surgery and others only matching skin incisions with no procedure performed at all. Two years later, the sham-surgery group reported no less pain and no worse function than the patients who'd actually been operated on. It remains one of medicine's starkest demonstrations of the placebo effect.

— J. Bruce Moseley et al., A Controlled Trial of Arthroscopic Surgery for Osteoarthritis of the Knee — New England Journal of Medicine, 2002