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So what happens when you crack your knuckles? Check out a study led by Dr. Robert Boutin, radiology professor at University of California Davis.

With the help of ultrasound imaging, the team has tried to crack the code of knuckle cracking.

"It's extremely common for joints to crack, pop and snap," Boutin said. "We were interested in pursuing this study because there's a raging debate about whether the knuckle-cracking sound results from a bubble popping in the joint or from a bubble being created in the joint."

They roped in 40 participants, with 23 men and 17 women aged 18 to 63 years old. About 30 of them would crack their knuckles about 20 times a day, although 10 had never done it.

At first they were asked to crack the base of their fingers, or the metacarpophalangeal joint, even as researchers captured them in audio and visual recordings, apart from the ultrasound imaging.

The fingers were studied for "range of motion, grip strength and laxity before and after the experiment," according to HNGN.

The recordings seemed to coincide with flashes of light just near the base of the fingers, captured in the ultrasound images 94 percent of the time.

"There have been several theories over the years and a fair amount of controversy about what's happening in the joint when it cracks," Boutin said. "We're confident that the cracking sound and bright flash on ultrasound are related to the dynamic changes in pressure associated with a gas bubble in the joint."

So is the sound of cracks due to "the bursting of a bubble or the creation of a bubble?"

Boudin believes that it is due to the latter, even though more research is needed, he conceded, according to The Washington Post.

They state that there do not seem to be any harmful effects of the knuckle-cracking, even in the long term.

The study was presented Tuesday at the annual meeting of the Radiological Society of North America.