Whether you hate cracking your knuckles or you do it 10 times a day, there have been a lot of urban myths and strange theories about what's actually happening inside your body to make that noise.
The science behind that noise, as it turns out, is pretty interesting, as the journal PLOS One revealed with this little experiment. Together with a team of researchers at the University of Alberta in Canada, they put chiropractor Jerome Fryer in an MRI machine, with a doohickey attached to his hand that would crack his knuckles for him. In case you're wondering why they chose him, here he is having the crack (we won't apologise for that joke, it was excellent).
With him hooked up to an MRI machine, the team were able to get a look at what actually happens when your knuckles (and probably other joints) crack, and they captured video of it too so we can all enjoy it.
Lead author of the study, Greg Kawchuk, explained exactly what was going on in the footage in a press release, and that the cracking noise you can hear is caused when the joints quickly move apart, creating a bubble of gas in the fluid that keeps them lubricated. "It's a little bit like forming a vacuum", he added. They believe that the small white dot (that can be seen on the footage forming just before the crack is made) could be water gathering in the joint before it pops.
While most scientists believe that cracking your knuckles is totally harmless, this research could help them find out for sure, and finally confirm that your mother was making up stories when she told you she knew a guy who cracked his knuckles all the time until one day he cracked them too hard and they all fell off. That's right, the knuckles, not the fingers.
