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Surprising Pain Science

Counterintuitive results and the fallibility of “common sense” about pain, injury, and rehab

updated (first published 2009)
by Paul Ingraham, Vancouver, Canadabio
I am a science writer and a former Registered Massage Therapist with a decade of experience treating tough pain cases. I was the Assistant Editor of ScienceBasedMedicine.org for several years. I’ve written hundreds of articles and several books, and I’m known for readable but heavily referenced analysis, with a touch of sass. I am a runner and ultimate player. • more about memore about PainScience.com

Sometimes I read a study & the results are all like waaaat????

There are a hundred ways that an idea can seem reasonable…even when it’s dead wrong. This article features some interesting examples of pain science that defy expectations and counter intuition.

Strange but true: unstable ankles should be stabilized

Getting people to use injured body parts as soon as possible is an important concept in rehabilitation, but it’s not a license to force injured anatomy to function before it’s ready for it. In the past, injuries were immobilized too much.1 In the last couple decades, this pendulum has swung too far the other way.

In 2009 the Lancet published results of an experiment showing that the widely practiced method of minimal bracing for severe ankle sprains simply doesn’t work.2 Instead, ripped up ankles should be put in a cast and given a chance to stabilize, rather than rushed back into action as quickly as possible.

Crazy, right? It may sound obvious when I put it like that, but it’s actually at odds with a powerful “common sense” trend in physical therapy. Right now, a great many people with seriously sprained ankles are still pushed to use them too hard, too soon, by professionals who haven’t gotten the memo. Crossfit gyms are full of people who think it’s perfectly logical to get that ankle doing its job again.

“This elegant study highlights the need for trials to address common problems,” the editors commented. In other words, we need to test all assumptions.

Will the real knee surgery patients please stand up?

EXCERPT This section is about knees, but it’s an excerpt from PainScience.com’s detailed low back pain tutorial, because it’s such a good example of an important concept. It’s anatomy agnostic.

One of the most surprising results in the relatively recent history of musculoskeletal medicine is a study conducted by the U.S. Veteran’s Administration in 2002.3 There have been several others like it since.

In this study, surgeons operated on three hundred people with osteoarthritis of the knee. Half were given a standard knee surgery, widely considered an effective solution for a clear, mechanical knee problem. The other half were given a bogus surgery: a probe was inserted into the knee and removed without doing anything. The patients had no idea if they’d had real surgery or not.

Incredibly, both groups experienced equal improvement in their knee pain.

The lead author, Dr. Lorimer Moseley, a bit of a rock star of a pain researcher from Australia, was quoted after publication, “We don’t really understand the placebo effect.” Understatement!

So placebo is a force to be reckoned with, and researchers need to compare all kinds of treatments with placebos and sham interventions whenever possible — but especially when the treatment is expensive or risky. Surgeons have been sloppy about this historically, typically doing “inbred” studies that compare only different kinds of surgeries, rather than comparing surgeries to sham surgeries and other kinds of therapeutic interventions, or to no intervention at all (another kind of control, less important to our discussion of placebo, but still important). This is the placebo problem with surgery. The same basic point is made in detail by a surgeon; in fact, he has devoted an entire blog to it.4 As he explains, you “need a placebo [surgery] trial when the outcomes are ‘soft’ (subjective: pain).” Need! It’s just the only way to know if a real surgery actually works on back pain. This is Research Methodology 101.

Slipped discs are rarely a big deal

The granddaddy of all assumptions in the science of aches and pains is the assumption that “slipped” or herniated intervertebral discs are a painful, degenerative problem. That assumption is baked into conventional wisdom in countless ways (like spine models that always have a bright red plastic herniation, the better to scare patients with).

Spine models always have a bright red plastic herniation, the better to scare patients with.

And yet the evidence is amazingly contrary to that assumption, and has been for many years now: the reality is that many people have herniated discs without pain, and even when they do it often spontaneously retracts and/or just stops hurting: “resorption.” In fact, most of them probably do — about 66%, according to a 2017 meta-analysis.5 In the popular and professional imagination, disc herniation is perceived as degenerative condition. People assume that discs, once they have “slipped,” are not going to un-slip anymore than a broken wine glass is going to jump off the floor and put itself back together. This attitude has been evident in most of the conversations I’ve ever had about back pain for my whole career. Almost every layperson has it, and a genuinely shocking number of professionals still seem to have it as well.

Herniated discs can be a big deal, especially in the short term, but the reality is in stark contrast to “common sense” — and much more hopeful!

Never trust common sense

The examples above (and many more) show that we need scientific testing to check any notion that we think is obvious or common sensical — they are as likely to be wrong as any other idea, maybe more. In my professional experience since 1997, physical therapy is rife with “common sense” that is either dubious or already mostly disproven. What seems like common sense is usually fashion and dogma and assumptions based on inadequate evidence.

Even when there is good evidence proving that the conventional wisdom is wrong … the conventional wisdom will still persist for years or even decades.

Calling for a little humility in health care is hardly original. But I think professionals need to go farther than a little humility. I think we need to get really comfortable — really, really comfortable — with saying “I don’t know” about practically everything. Contrary to what we’d all like to believe, the science of pain and injury is still pretty primitive. After all, we’re still just finding out how to treat an ankle sprain! How long do you think it’s going to take for every doctor and physiotherapist to find out about that research and apply it?

Meanwhile, how many millions of people will be told that it is “common sense” to get that sprained ankle working again as fast as possible?


About Paul Ingraham

Headshot of Paul Ingraham, short hair, neat beard, suit jacket.

I am a science writer, former massage therapist, and I was the assistant editor at ScienceBasedMedicine.org for several years. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook or Twitter.

What’s new in this article?

MarchMinor science update: ugpraded a citation.

Notes

  1. See the great story about my father’s somewhat miraculous gunshot wound rehab near the beginning of Mobilize! BACK TO TEXT
  2. Lamb SE, Marsh JL, Hutton JL, Nakash R, Cooke MW. Mechanical supports for acute, severe ankle sprain: a pragmatic, multicentre, randomised controlled trial. Lancet. 2009 Feb 14;373(9663):575–581. PubMed #19217992. BACK TO TEXT
  3. Moseley JB, O’Malley K, Petersen NJ, et al. A controlled trial of arthroscopic surgery for osteoarthritis of the knee. N Engl J Med. 2002 Jul 11;347(2):81–8. PubMed #12110735. PainSci #56845. BACK TO TEXT
  4. Doctorskeptic.blogspot.ca [Internet]. Skeptic D. Doctor Skeptic: Why placebo surgery is ethical, and necessary; 2012 Nov 29 [cited 17 Dec 9]. BACK TO TEXT
  5. Zhong M, Liu JT, Jiang H, et al. Incidence of Spontaneous Resorption of Lumbar Disc Herniation: A Meta-Analysis. Pain Physician. 2017;20(1):E45–E52. PubMed #28072796. PainSci #53529.

    Once a spinal disc has “slipped,” it seems like it’s in a biomechanically awkward situation and can’t recover any more than a broken window can reassemble itself. And yet several studies — like Kjaer 2016, which followed dozens of patients for eight years — have suggested that herniated discs spontaneously de-herniate!

    This paper (Zhong et al) is the first meta-analysis of those studies. The pooled data from eleven of them shows an extremely high overall incidence of disk resorption: a whopping 66% in patients who received conservative therapy (anything but surgery). This adds to the already large pile of evidence that back pain’s bark is usually much worse than its bite, and MRI and x-ray are almost useless for most low back pain.

    More study is needed — of course, as always — because none of these studies were randomized controlled trials, and there was barely enough data for meta-analysis. However, the final number is so high that it’s safe to assume that approximately “lots” of herniations resolve on their own.

    As if this wasn’t counter-intuitive enough already, the worst herniations are actually the most likely to regress (see Chiu et al). The temptation to assume the opposite is hard to resist, but “common sense” is useless in musculoskeletal medicine, a field where there seem to be no safe assumptions.

    Does this data show that “conservative therapy” is the key to resorption? Unfortunately not: “conservative therapy” is vague to the point of being meaningless here. All it does mean is that these patients were treated with anything but surgery (or injections). We already suspect that resorption occurs whether people receive any treatment or not (Kjaer again), and we know that there are no clearly effective therapies for back pain at all (Machado). The only thing we can tell from this paper is that many herniations resolve without surgery, not that therapy fixes herniations.

    BACK TO TEXT