Joint Cracking – What is that sound?
You’ve all heard a joint cracking. You’ve probably even pulled your finger to make those joints crack- after-all it typically feels pretty good after! If you have ever been to a Chiropractor and had your spine adjusted, you have probably heard a similar cracking sound. If you haven’t been to a Chiropractor, perhaps you were nervous as to what was causing that cracking noise (but I’ll let you in on a secret, it certainly isn’t bones breaking!)
For years, the source of joint cracking was a mystery. We knew that it happened when you adjusted a joint (gapping the joint to allow for more movement), but we didn’t know what caused that noise. As of April 2015, thanks to Dr. Greg Kawchuk and his team at the University of Alberta, we now have an answer to this important question!
Dr. Kawchuk’s Study
Using an MRI (magnetic resonance imaging), a device was attached to the fingers of one subject that was designed to pull on the finger with the same force every time. While the finger was pulled on, the MRI captured the joint and how pulling on the finger allowed not only the joint space to increase, but it captured the event that caused the cracking noise!
The cracking noise we hear is all because of a process called Tribonucleation. Tribonucleation is a mechanism that creates small gas bubbles as a result of breaking contact 2 solid surfaces (the two bones that make up the joint) immersed in a liquid that contains dissolved gas (synovial fluid-this is a nutritious fluid that lubricates and protects our joints, sort of like the WD40 of our body!)
As the finger was pulled on the joint space slowly increased, until a point where the cracking occurred, which signalled a period of rapid expansion of joint space. The cracking noise was heard at the same time as a gas bubble was formed inside the joint. Even after the cracking noise had subsided, the gas bubble still persisted inside the joint provided the joint was still being distracted (aka the finger was still being pulled).
The image above shows an MRI of the left hand. The image on the left is the hand before the index finger is pulled on. The image on the right is showing AFTER the finger has been pulled on, and you can see that yellow arrow is pointing to a black smudge- THAT’s THE BUBBLE responsible for the cracking noise! Cool hey?
This youtube video shows the creation of the gas bubble that formed as the joint cracking happens!
Bottom Line? The cracking that happens with an adjustment of the finger (or spine for that matter), is a result of a gas bubble forming within the joint. That’s it! A little gas bubble is responsible for causing that noise you hear! So rest assured, the next time you visit your Chiropractor for an adjustment that noise you are hearing is perfectly normal, and is in no way the sound of of bones breaking or snapping! In fact, it is likely that the noise can signal that the joints in your spine have been ‘gapped’ or allowed to move more freely, which is the aim of adjusting the spine or joints of the body!
As the saying goes, “Motion is Lotion”, so the more we are able to keep our joints moving throughout our body, the less painful and happier our bodies and joints are! Adjusting the spine and joints of the body is a fantastic way to keep our joints well ‘lubricated’ and ready to continue living a healthy and active lifestyle! And, most importantly, you now know where that cracking sound is coming from!
Dr. Elaine Screaton (DC, BSc) is a Chiropractor currently practicing at Synergea Family Health Centre in Calgary, Alberta.
- Kawchuk, G. N., Fryer, J., Jaremko, J. L., Zeng, H., Rowe, L., & Thompson, R. (2015). Real-Time Visualization of Joint Cavitation.