Pop! Goes the Knuckle — but Why?

Ever wonder what makes that popping noise when you crack your knuckles? The answer is finally here! And even better, Live Science has a video so you can even see what’s happening when you crack your knuckles through a MRI scan.

This article says that by “using MRI to video-record knuckle cracking in action, researchers have discovered that the unsettling ‘pop’ made by cracking one’s knuckles results from the rapid creation of a cavity in the fluid inside the joints.”

Study researcher Greg Kawchuk, professor of rehabilitation medicine at the University of Alberta in Canada, says it’s like forming a vacuum. “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.”

Kawchuk and his colleagues put together a study called “Pull my Finger,” after a new hypothesis arose having to do with the popping phenomenon we all experience.

Over the last few decades, researchers have speculated that pulling apart your finger joints creates or collapses bubbles in the joint fluid.

So far, there seems to be no worries about hurting oneself by continuing to crack your knuckles, other than potentially making those around you cringe at the sound.

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