Does the knee surgery work, or just the belief in it?

Question

Patients who undergo a popular knee operation report less pain afterward, and surgeons take this as proof the procedure works. A research team proposes a startling control: some volunteers get a "sham" surgery, an anesthetic and a small incision but none of the actual repair.

Why would a serious trial include a fake surgery, and what does the comparison isolate?

Accepted Answer

Surgery carries a huge placebo effect. The whole ritual, anesthesia, an incision, recovery, and the strong belief that a problem has been fixed, can by itself reduce reported pain, sometimes for months. If you only compare operated patients to their former selves, or to people who declined surgery, you cannot tell the physical repair from this powerful expectation. People who chose surgery also differ from those who declined, adding self-selection on top. Why a sham control. Giving some randomly chosen volunteers a convincing but empty procedure holds the entire placebo ritual equal across bo…

Does the knee surgery work, or just the belief in it?

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