Cracking things is something that so many of us do without ever thinking about what is actually happening. This article will hopefully give the reader a better understanding of what is happening when that knuckle or neck or back 'cracks.'
When two bones are attached to each other they are called a joint. They are held together by a capsule. In the middle of the joint is fluid called synovial fluid.
When a joint cracks, or cavitates as science would say, a small gas bubble is sucked into the middle of the joint. This happens when the two sides of the joint are slightly separated.
These ‘cavitations’ cannot be repeated immediately as the gas can take 20-30min to dissipate.
But cracks can also occur when a tendon flicks over a joint or when you roll you shoulders and a cracking noise occurs.
These cracks can be repeated over and over with the movement that causes them because there is no gas involved.
So Is It Bad To Cause A Cavitation or To Have a Tendon Flick Over?
Sort of yes and sort of no.
In practise I see at least one person a week with an acute pain in their neck. They’ve turned their head quickly, felt something ‘go’ and cannot turn their head without exquisite pain.
This is most commonly a joint sprain and will ease within a few days.
But what is interesting clinically is how often the person then explains that they can usually click their neck and it feels better but now they can’t get the click.
When asked if the joint they are trying to crack feels like where the pain is, they almost always will say “Well yeah sort of, maybe.”
So How is Cracking Your Neck Frequently Related to Neck Pain?
When you crack a joint you suck a gas bubble into the joint.
This opens the joint up and makes it feel great, for 20-30min, but then the gas dissipates and the joint goes back to normal.
If a joint is expanded by a gas bubble the two bones that the joint holds together are pulled apart ever so slightly.
Which means that the ligaments/joint capsule that holds the two bones together get stretched ever so slightly. Which in isolation, or infrequently, doesn’t really matter.
But when it becomes important is when you repeatedly do it.
With repetitious cracking, repetitious opening of the joint occurs, repetitious ever so slight stretching of the ligaments occur.
If the ligaments/joint capsule that holds the two bones together get stretched too frequently they become a bit lax, a bit looser than they should.
So What Does It Matter If The Ligaments/Joint Capsule Get a Little Bit Looser? It Feels Gooooood.
The brain, which is like the big boss of the body, is always receiving information about what the body is up to.
If it receives information that a joint is not as well protected from forces as it should be, maybe because the ligaments have been repeatedly mild stretched, then it will do something to protect that joint.
It will contract muscles around that joint to do the job that the ligaments are supposed to do.
Which is a good idea by the brain except that it compresses the joint, making it feel “tight.”
And if you’ve been able to crack that sensation away in the past you are likely to crack it again.
Which would place a gas bubble in the joint, which would every so slightly stretch the ligaments/joint capsule that holds the joint in place, which means the muscles the brain has told to protect the joint will relax as once again the ligaments are able to do their job.
But once that gas bubble has dissipated the brain once again will tighten the surrounding muscles to protect the joint.
And the cycle continues….
So What About When An Osteo/Physio/Chiro/GP Does It?
I can only answer for the Osteopaths here.
Osteopaths will look for a joint that is being compressed, one where the muscles are contracted around it. And if it needs a gas bubble they will use a technique that can create it.
They will also ask if you have been cracking the area that is sore. If they find out that you have been cracking the joint that is sore they are unlikely to crack that joint again as it will perpetuate the cycle explained above.
What If My Osteo/Chiro/Physio/GP Is Always Cracking the Same Joint?
Well you should probably get a second opinion as they are likely perpetuating your pain paradigm.
That is, if the practitioner is repeatedly cracking the same joint they are not looking for the reason that that joint is getting sore.
It may be that you yourself are already cracking that joint. It may be that you are sitting with your nostrils fogging up your computer screen and cricking your neck. It may be that they themselves are ever so slightly stretching the ligaments/joint capsule themselves by repeatedly cracking the same joint.
Whatever the case, if you feel that your practitioner is regularly cracking the same joint and that you are regularly still getting sore in that area you should get a second opinion.
And What About That Crack That I Can Repeat Over and Over?
Stop doing it. Go and see your therapist and work them to figure out why there is a crack sound every time you lift your thigh, or every time you roll your shoulders.
A great video that shows an MRI of a knuckle being cracked is available