The evidence on Botox for muscle knots blew my mind once upon a time

Way back in 2007, a study rocked my world. This when I first really getting going with PainScience.com, and I could see the light at the end of the strange tunnel of my clinical career as an Registered Massage Therapist. And that blasted study clearly showed something that seemed just about impossible to me back then: “current evidence does not support the use of Botulinum toxin A injection in trigger points [muscle knots].” What?! 🤯

The truth is ultimately never bad news, of course, and I’m going to use this as an example of honouring the evidence even when it irritates me.

And it really irritated me. In fact, that might have been my first ever major experience with evidence that seemed to be bullying my beliefs. During my early years as a massage therapist — and under the influence of more mentorship than science — I had been working with the strong assumption that Botox injection just flipped the switch on trigger points, just turned ‘em off completely, zap, done, “deactivated” — no more trigger point until the Botox wears off! I believed Botox would work because I had fully accepted a hypothesis about how trigger points work. And if that hypothesis was true, then Botox had to work.

(Need a Botox refresher? I dedicated a post to the stuff about a year ago. Or a “trigger points” refresher? That’s a much bigger topic: See the PainScience.com index of trigger point articles.)

Just because I thought Botox would do the job didn’t necessarily mean I thought it a wise treatment option for patients, of course. We are talking about injecting one of the most deadly toxins known. It’s invasive! There are risks! It’s difficult to reliably inject the actual trigger point! (Some would say impossible, but I’m not getting into that today.) And so on.

But the evidence of the effect of Botox on trigger points was super important theoretically, because — if it worked — it would elegantly prove something vital about the physiology of trigger points. Botox blocks the release of the neurotransmitter acetylcholine, making it actually impossible for muscle to contract. And so, if Botox stops a trigger point, that would strongly suggest (at the very least) that a trigger point is basically a nasty little cramp. If you know how to break a trigger point, then you know how it works. Such evidence would have really helped to push back the scientific darkness around muscle pain.

No such luck. Ho and Tan’s review didn’t necessarily show that Botox can’t deactivate trigger points in principle. For instance, Botox might do exactly what I thought it would when injected accurately… but it could be so difficult for practitioners to reliably inject it into exactly the right place that it is also highly unreliable as a treatment.

But it certainly did mean that its usefulness as a treatment was underwhelming.

Evidence since 2007? Not much!

The data was “limited” back in 2007, of course, and unfortunately that hasn’t changed much. Gerwin pointed out in 2012 that “few studies have been designed to avoid many of the pitfalls associated with a trial of botulinum toxin treatment of trigger points.” In 2014, the most recent Cochrane review reported that the evidence was slightly positive but “inconclusive,” based on only four studies at that time, and too different for data-pooling. Also in 2014, Zhou and Wang thought that there were a few “well-designed clinical trials to support the efficacy of trigger-point injections with Botox for myofascial pain syndrome” — but still reported lukewarm results, damning with faint praise.

And there hasn’t been much more evidence to analyze since then.

A weak signal from a weak body of evidence isn’t an “absence of evidence.” When just a few trials have barely positive results, that’s much closer to actual “evidence of absence.”

I’ve had seventeen years to get used to the fact that Botox probably doesn’t work for trigger points in principle, or at least in practice, but I still find the evidence a bit irritating. I accept it, but I still don’t like it. Beliefs are sticky!

There’s a chapter about Botox injection in my trigger points book. This free blog post reproduces the heart of it, but there’s more detail in the book.