This is What Happens When You Crack Your Knuckles

Forget what your mother told you. Cracking your knuckles may not be so bad for you after all.

boy-cracking-knuckles
Photo by Ben Javens

You've probably heard that cracking your knuckles causes joint pain or even arthritis. And while scientists have said for a while that doesn't seem to be true, the myth lives on. Now, a new study looks at what actually happens when you crack your joints.

Researchers from the University of Alberta​ wanted to better explore the cause of that popping sound. To do so, they set out to visualize what it looks like inside your body when you crack a joint. One of the lead researchers, Jerome Fryer​, hooked his finger up to a tube that pulled, cracking his knuckle, and simutaneously recorded it using an MRI. 

So what actually happens when you crack your knuckles? A small bubble of gas forms between your joints in the synovial fluid, which is the slippery lubrication between your joints. “It’s a little bit like forming a vacuum,” Greg Kawchuk, lead author of the paper, said in a statement. “As the joint surfaces suddenly separate, there is no more fluid available to fill the increasing joint volume, so a cavity is created and that event is what’s associated with the sound.”​ 

This is what it looks like:

 

 

Next, the researchers plan to dive deeper into what that cracking actually does to the joint and what it says about the state of your joints. “The ability to crack your knuckles could be related to joint health,” Kawchuk said in the statement. “It may be that we can use this new discovery to see when joint problems begin long before symptoms start, which would give patients and clinicians the possibility of addressing joint problems before they begin.”