A study published this month nicknamed the ‘pull my finger study’ purportedly shows the first ever MRI footage of joints being cracked. This look at knuckles being cracked under an MRI has shown scientists for the first time just what it is that’s causing the popping sounds when knuckles and joints are cracked. If the six-second video above doesn’t agree with your stomach and you find yourself being nauseous, know that you’re not alone, this footage is unsettling for a lot of pansies.
The University of Alberta’s ‘Faculty of Rehabilitation Medicine’ published the finding on just what causes the ‘crack’ and ‘pop’ of your joints and fingers:
The idea for the project was born when Nanaimo chiropractor Jerome Fryer approached Kawchuk about a new knuckle-cracking theory. They decided to skip the theories and, with U of A colleagues Jacob Jaremko, Hongbo Zeng, Richard Thompson and Australian Lindsay Rowe, decided to actually look inside the joint.
But to find an answer, the team needed someone capable of cracking knuckles on demand—a job that fell to Fryer himself. Kawchuk said most people have the ability to crack their knuckles but unlike most, Fryer can do it in every finger, and after the standard recuperation time, he can do it again.
“Fryer is so gifted at it, it was like having the Wayne Gretzky of knuckle cracking on our team,” says Kawchuk.
Fryer’s fingers were inserted one at a time into a tube connected to a cable that was slowly pulled until the knuckle joint cracked. MRI video captured each crack in real time—occurring in less than 310 milliseconds.
In every instance, the cracking and joint separation was associated with the rapid creation of a gas-filled cavity within the synovial fluid, a super-slippery substance that lubricates the joints.
“It’s a little bit like forming a vacuum,” Kawchuk said. “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.”
And now that you all know how the cracking of knuckles and joints is caused, here’s the footage on repeat in an animated GIF:
Also, for those of you forgot that I’m the editor with the weird ass hand, here’s a GIF of me bending me fingers backwards (video here):