Joint movement and the refractory period

Chiropractors often crack joints to elicit joint movement, improve the joint spacing and a multitude of other effects including improving neurological function.

I personally have never liked the ‘crack’ word because it insinuates that something is breaking. This isn’t so and prefer to call it the ‘audible release’. This is a better phrase because it indicates a release of joint tension.

So what happens after the joint is released and expels a popping sound? This has been a passion of mine since the very day I decided to become a chiropractor. Over the 15 years of being a chiropractor, I have always been curious on the exact mechanisms as to why I get patients better. We know that a chiropractic adjustment which elicits the sound, improves joint positioning and alignment but can we do more with our treatments?  Can we make our treatments even more effective and longer lasting?

Chiropractic is growing in research and I am happy to have the opportunity to be contributing. In a recent publication, I was an author (and subject) to investigate where that noise is coming from specifically, which believe it or not, has not been specifically shown. Excitingly, our publication went viral. You can read the publication here in PLOS One, or you can listen to a couple interviews I did with CBC radio and also the Jill Bennet Show. There were over 500 media stories including articles in the Guardian and New York Times. It was a big hit. Just google: “knuckle cracking study April 15, 2015 and News”.

To investigate the audible release of a spinal joint, the knuckle joint is the most researched because is has all the anatomical components of a spinal joint. And importantly, it is easy to access because it doesn’t have a lot of of tissues surrounding it. Our research team was able to use MRI to see a live finger pulling (which was me, see below) to the point of an audible release. This had never been done before. You can see the experimental set-up below.

If you would like to watch the live MRI video as my finger is being pulled to the point of an audible release, you can see that here. 

Increased Joint Movement After an Audible Release

Like all joints after they release and go pop, one cannot repeat this for a certain period of time. The period of time in which you have to wait to make the joint go ‘pop’ again is known as the refractory period. And during this time, the joint has increased joint movement. This increased joint movement takes the joint into a range of movement that is greater than normal. active movement. This increased range of motion is called the paraphysiological space and you can see that shaded grey area in the image below.

This space provides an opportunity to improve flexibility and nutrient fluid flow. In practice, I  often use this increased joint movement when I would like to access discs for treatment, for example–encouraging nutrient influx to compressed discs. Currently, I am working on a model to help explain this increased movement in hopes to understand more about the paraphysiological space and whether we can improve our outcomes even further as chiropractors.