Why Your Knuckles 'Pop'

Next time you 'pop' your fingers, you know that the distinctive sounds you hear is because of the cavities that have formed inside the joints of the fingers, say scientists according to research in Journal Plos One.

"We call it the 'pull my finger study' - and actually pulled on someone's finger and filmed what happens in the MRI. When you do that, you can actually see very clearly what is happening inside the joints," said lead author Greg Kawchuk, a professor at the University of Alberta.

Right back to 1947, scientists have debated why knuckles pop and crack, when UK researchers came up with theories that vapour bubbles were formed. However, they were questioned in the 1970s, when one more team said that collapsing bubbles were the reason, according to huffingtonpost.

The real idea popped up when Nanaimo chiropractor Jerome Fryer came up with a new theory, and agreed to keep cracking his knuckles on every finger. He put his fingers inside a tube that was connected to a cable pulled into the tube till the joints cracked. MRI videos captured every crack in less than 310 milliseconds.

Every crack and joint separation "was associated with the rapid creation of a gas-filled cavity within the synovial fluid, a super-slippery substance that lubricates the joints," according to thehuffingtonpost

Kawchuk describes how each crack was created when the joints separated, while gas-filled pockets came into the synovial fluid between the joints. The bubble is formed in the gas emerging from the fluid as the pressure plummets in it, just as bubbles fizz up in bottles. "If you've ever washed up glass plates, you'll know they can be hard to separate when they are wet. The film of water between them creates a tension that needs to be overcome. It's similar with joints. When you pull on them, they resist at first, and then suddenly give way," said Kawchuck, according to theguardian.

"It's a little bit 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 said.

The findings lead to some research into the advantages as well as minus points of joint cracking, said Kawchuk.

Scientists assess that cracking your knuckles draws in energy enough that harms hard surfaces, yet the knuckle-cracking does no harm!

"The ability to crack your knuckles could be related to joint health," said Kawchuk. He feels that they hold the key to the problems with other joints in the body, including the spine, which indicate why they get arthritic or injured.