Here’s What Happens When You Crack Your Knuckles

knuckle cavity

There are two kinds of people in the world: Those who feel a great relief from cracking their knuckles, and those who squirm at just the thought of it.

Scientists have long debated the the cause of joint cracking, and there’s a lot of confusion about whether or not it can damage the hand (the answer is: probably not!). Now, they’re finally beginning to settle the debate about what physically happens when someone says “pull my finger.”

In a recent study published in PLOS ONE, a group of researchers found that cracking a knuckle forms a temporary cavity in the body, disproving a long prevalent theory that the crack is due to the collapse of a bubble. The study focused on the fingers of Canadian chiropractor Jerome Fryer, who has the ability to crack the knuckles in every one of his fingers on demand (not everyone can). He also has a particular interest in the science behind knuckle cracking.

“Fryer is so gifted at it, it was like having the Wayne Gretzky of knuckle cracking on our team,” said Greg Kawchuk, the study’s lead author and a professor of rehabilitation medicine at the University of Alberta, in a statement released by the school.

To observe what was happening when his knuckles cracked, Fryer inserted each of his fingers into a tube connected to a cable that was slowly pulled until his knuckle joint cracked. An MRI video captured each knuckle joint crack in real time.

The researchers observed the same phenomenon occurring in every one of Fryer’s fingers: when a joint separated and made the “cracking” sound, a gas-filled cavity formed within the synovial fluid, a slick substance that lubricates the joints.

“It’s a little bit —> Read More