Single Blind Study – Scientific Reasoning in the Clinical Exam (Part 2)

So we all know that our patients experience pain relief from many placebo based mechanisms. A little bit of joint cracking, needle tapping, and (insert modality here) can go a long way towards providing a patient some temporary relief which gets us to our main goal of restoring movement.

There has been decades of research on the aspects of placebo:

  • 2 sugar pills better than 1 for reducing gastric ulcers(1)
  • 1 injection better than 2 sugar pills for reducing gastric ulcers(1)
  • Higher priced items are more effective than cheaper ones, but only when people know they are the higher priced meds.(1)

Just more fun facts…

  • Sham surgeries for Knee OA & degenerative meniscus – no difference between groups (even at follow-up of 2 years!) (2,3)
  • Sham shunts place for Meniere’s disease – no difference between groups at 4 years (4)
  • hypertrophic obstructive cardiomyopathy w/ implantation of inactive pacemakers – both groups saw significant decrease in angina, dyspnea, palpitations, and LV tract outflow gradient (i.e. their hearts worked better…from nothing) (5)

Placebo, the translation from latin, “I shall please.” It’s a pretty cool thing, and I use it to my advantage quite often when treating patients. But what happens when this bio-psychological influence we have over our patients goes awry?

“I will harm.”

No one would say that to their patient, but do you do it? The “Nocebo” is, in essence, the alter-ego of the placebo. It’s the mean spirited evil-twin, if you will. It mainly comes in the form of intention or implication. In other words, you don’t have to slip a patient a pill that tells them their knee OA pain wont get any better…you just imply it (I hope you don’t say it!!).

Now, you might say, “well that’s hardly an issue. I obviously wouldn’t intentionally harm my patient by providing them with a pill or a cream or an exercise that would make them feel worse..” but that’s just the point…isn’t it? Again, nocebo’s are rarely ever physically provided, and even so (as you’ll see in a few moments) they only hold any power through the context and implication through which they are given.

Recent blogs have covered this topic of the language we use with our patients: Hey, Adam and Martin!, and this important piece about reconceptualizing pain from Jørgen Jevne at the BJSM.

But this post is specific. We’re talking about being better at the examination process; and for that my friends, the advice is simple: Blind your patients.

Yes, blind them. Don’t tell them exactly what you’re purpose is for doing things.

Why? Because probably 80% (just a guess) of our examination procedures are tailored around provoking pain. If you tell a patient who came to you with pain, and is concerned about his or her pain, that you’re going to poke and prod and do things that might make them hurt…well don’t you think the odds and frequency of that patient hurting go up?

The nocebo is a real thing and we need to recognize its potential to affect our diagnostic accuracy, not just the outcome with the patient. That patient who is anxious about moving or fearful of your hands near a painful area may just experience even more pain at the thought of it, or worse yet, you implying such things.

Patients in two groups were studied under fMRI.(6) They had a standard lotion/cream applied to their skin and subsequent application of heat via a hair dryer. The difference between group experiences was that one group was told the cream had capsaicin (it was also on the label), while the other group was just told it was standard cream (because it was…in both groups).

The result? It was significant–not just for subjective pain report, but for neuronal activity in the spinal cord (the cortex activity in relation to nocebo has already been established). All because these patients thought that heat intensifying capsaicin was in their lotion.



This is a real, physiological response to your suggestion. Your implication. This is a big deal. And if you’re saying one of these two things: 1) “Oh come on! Their real issue will be easily distinguishable from this “created” pain.” OR 2) “Yeah, yeah. We were told back in school not to lead our patients during pain provocation procedures. Tell me something I don’t know.”

I would ask you to consider your bias (Read Part 1). Think about the potential for major diagnostic error when you imply that a certain procedure will hurt (either through your words or behavior) all because you have a strong notion that this potential issue is part of the patient’s pain problem. You have anchored down already.

Still not convinced, watch this:


Check in next week for the final installment in the SRICE Series.


(PS- Yeah, this was mainly an excuse to highlight some cool placebo and nocebo studies…but what do you expect?? This is the #PTBT!)


Some references:

1) Arnold MH, Finiss DG, Kerridge I. Medicine’s inconvenient truth: the placebo and nocebo effect. Internal Med J. 2014;44: 398-405.

2) Sihvonen R,Paavola M, Malmivaara A, et al. Arthroscopic Partial Meniscectomy versus Sham Surgery for a Degenerative Meniscal Tear. N Engl J Med. 2013; 369:2515-24.

3) Moseley B, O’Malley K, Petersen J, et al. A Controlled Trial of Arthroscopic Surgery for Osteoarthritis of the Knee. N Engl J Med. 2002; 347(2):81-88.

4) Thomsen J, Bretlau P, Tos M, Johnsen NJ. Placebo effect in surgery for Meniere’s disease. a double-blind, placebo-controlled study on endolymphatic sac shunt surgery. JAMA. 1981; 107: 271–7.

5) Linde C, Gadler F, Kappenberger L, Ryden L. Placebo effect of pacemaker implantation in obstructive hypertrophic cardiomyopathy. Am J Cardiol. 1999; 83: 903–7.

6) Geuter S, Buchel C. Facilitation of Pain in the Human Spinal Cord by Nocebo Treatment. Journal Neurosci. 2013; 33(34):13784-13790.





4 thoughts on “Single Blind Study – Scientific Reasoning in the Clinical Exam (Part 2)

  1. Pingback: Are you biased, bro? – Scientific Reasoning in the Clinical Exam (Part I) | PTbraintrust

  2. Pingback: The Best Special Test – Scientific Reasoning in the Clinical Exam (Part 3) | PTbraintrust

  3. Pingback: V O M I T | PTbraintrust

  4. Pingback: A Year in Review | PTbraintrust

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