Placebo effects and surgical superstitions

It's funny how the mind works. The placebo effect remains an unknowable mystery, where the body somehow compensates for an expected effect even in cases where the subject is aware that they are receiving a placebo. On an equally mysterious topic, I was deeply surprised when I first discovered the serious consideration with which some bizarre superstitions were treated in the healthcare field.

• A controlled trial of arthroscopic surgery for osteoarthritis of the knee (2002) shows that a placebo effect exists for osteoarthritic patients who undergo (or don't) arthroscopic surgery of the knee to relieve pain and improve knee function.
• The moon and the stones. Can the moon’s attractive forces cause renal colic? (2002) The answer is cautious: "The forces are negligible and not strong enough to be a physiological stimulus and cause renal colic. We are aware that our study at this point, because it was performed with a limited number of patients, can not be significant."
• Lunar phases and zodiac signs do not influence quality of radical cystectomy—a statistical analysis of 452 patients with invasive bladder cancer (2007) presents a much larger study and state: "Although this was not a prospective randomized trial, the statistical magnitude of the results do not support any recommendations for scheduling patients for radical cystectomy at any particular day of the lunar phase."
• Popular belief meets surgical reality: impact of lunar phases, Friday the 13th and zodiac signs on emergency operations and intraoperative blood loss (2011) couches the conclusion more emphatically: "Scientific analysis of our data does not support the belief that moon phases, zodiac signs, or Friday 13th influence surgical blood loss and emergency frequency. Our data indicate that such beliefs are myths far beyond reality." But in a move that cynical observers might suggest stems from a desire for continued funding, they end with: "So far, however, studies with adequate power and sample size calculation rejecting any association between superstition and medicine are under-represented in the medical literature."