There is every reason to believe that surgery is especially prone to placebo effects. The more dramatic the procedure, the more likely it raises hope of cure. "Quick, operate before the patient gets better" is one of those jokes that orthopedic surgeons tell among themselves, barely covering a hard truth: that a lot of elective surgery might be unnecessary or even harmful.
The evening after knee replacement surgery, I was startled to see the size of my right leg. Having been sliced and diced, stitched and stapled, it was seemed as if I had gained ten pounds, all in that leg.