Researchers Used This Live MRI Footage Of A Knuckle Cracking To Disprove A Popular Theory

Researchers at the University of Alberta recently addressed one question that’s been baffling the scientific community since the first caveman draped a white labcoat-looking fur over his shoulders and stroked his chin in deep thought: “Whaaaaaaat’s up with knuckle cracking?”

To get to the bottom of it all, the researchers set up an MRI and captured live video of a knuckle cracking by using a cable to pull the subject’s finger. From WRTV:

In the video, the knuckle joint separates, and a bubble of gas forms inside the slippery synovial fluid between the bones. Each crack lasts about one-third of a second.

But the bubble doesn’t burst. It’s re-absorbed during a 20-minute rest period where cracking is no longer possible. The researchers concluded that the cracking sound is caused by the rapid separation of the joint, not a breaking of the bubble as was previously believed.

The study’s author went on to explain: “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.” So, that settles that, I guess. The sound isn’t caused by bursting bubbles, or, as I had originally assumed, tiny dynamite explosions rigged up by lunatic miniature gremlins that live inside our hands. We are learning so much today.

(Via WRTV)

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