So, this is what actually happens when you crack your knuckles.

For some, it’s the most satisfying sound in the world, for others it’s stomach turning.

That little “Pop!” has finally been explained, with doctors discovering exactly what happens when you crack your knuckles.

In a new study published this week, Greg Kawchuk from the University of Alberta, and his international team of researchers used MRI technology to capture joint cracking as it happened. Canadian chiropractor Jerome Fryer, a champion knuckle-cracker himself was the test subject (how’s that for an entry on your CV…)

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Each of Fryer’s fingers were slowly pulled until they cracked. The MRI recorded precisely what was happening inside joint with each pull. The journal, published by  PLOS ONE on Wednesday, says that the images indicated the rapid formation of a cavity in the fluid between the joints.

Kawchuk said in a statement, “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.”

You may have thought, like many of us, and many scientists, that the noise of knuckle cracking was caused by the release of trapped air from the joint. The reality is the opposite.

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Suzanne Snodgrass, associate professor at the University of Newcastle told the Sydney Morning Herald, it was previously suggested that the joint-cracking sound was caused by a sudden change in pressure, as dissolved gases inside the synovial fluid rush into the joint creating a gas bubble that collapses to make a “crack.”

“This is what we [taught] students before this paper,” she said.

“We might change that now.”

The next step for Dr Kawchuck and the university’s research team is an investigation into the potential harms or benefits of joint cracking.

Scientists have previously calculated that the force with which you crack your digits may cause damage to hard surfaces, however research also indicated that long term, habitual cracking does not have any lasting negative affects.

So next time your mother or partner scolds you for partaking in some light knuckle cracking, be sure to let them know that at this stage, medical advice is inconclusive, but Dr Kawchuck it working on it.

Knuckle cracking, nail biting, loud chewing… What are your worst habits?