Pull my Finger - the crack

I always hold my breath when I tell people what I do for a living – as often as not when I say I’m a chiropractor the response is – oh you crack backs! Once realizing this they are often so excited to tell me their injury story and that they love their chiropractor and it feels great or... I see an odd look in their eye as they respectfully say they don’t think they could ever see a chiropractor because the cracking scares them!

I don’t blame them, if you don’t understand what the noise is that often but not always accompanies a chiropractic adjustment, it is a little scary. Often my first visit with a new patient I can spend as much time explaining what to expect with a treatment as I have spent examining and diagnosing the injury. As a patient it is important to understand any treatment that you undergo/agree to.

So what is the crack?
The scientific name for the crack is a cavitation. When you do an adjustment you are increasing the movement of a joint, when you do this a ‘gap’ or slight opening in the joint occurs and this causes a gas to form and this makes a popping or cracking noise. It is the same phenomena when you ‘crack’ your knuckles – and despite what your mom told you, you will not get arthritis from cracking your knuckles.

For years we knew that the noise was caused by a gas, but we incorrectly thought it was a gas dissolving or releasing until a very ‘landmark’ research paper was produced last year titled “PULL MY FINGER”. Landmark not because the discovery was noble prize worthy, but landmark because it made Almetric's top 100 research papers of 2015. https://www.altmetric.com/top100/2015/#explore

Due to the advanced technology we now have with MRI, the researchers at the University of Alberta were able to take an image of a patients finger joint being ‘pulled’, and in the moment when the cracking noise occurred they saw a gas bubble in the joint form. There was no breaking of structures or cracked bones – just gas.