Placebos are important. It's how science determines whether medical treatments are inherently beneficial. And for drug research, it's easy — you just use a sugar pill, or something with a harmless side effect. But what about surgery? That's trickier, but still doable. Surgeons just make an incision, then fiddle around for awhile like they're performing an operation, then close it up.
It's called sham surgery, and it works as a surgical placebo. It's ethically complicated, so there haven't been that many placebo-controlled studies of surgical procedures. But those few studies have shocking results. Consider: each year more than 500,000 Americans get arthroscopic surgery for osteoarthritis of the knee, and 700,000 get similar procedures for meniscal tears.
And as Aaron Carroll explains, both of these procedures are no better than placebo. --Ryan Cooper