You've probably heard about how 'bad' it can be for someone to regularly crack their knuckles, or any other joints in their body, for that matter.
It's long been perceived as one of the worst habits you can have, as many believe that you may increase the risk of developing arthritis every time one of your joints makes that popping noise.
You might enjoy the feeling you experience with cracking your joints, with simulations showing exactly what happens to your bones when you do it.
While many studies have been carried out into the addictive habit to uncover the truth behind it, many aren't aware of the health effects that come with cracking your knuckles.
Advert
A doctor has revealed what really happens though, explaining all the ins and outs in a YouTube video so all knuckle-crackers can be clued up on their daily practice.
What causes joints to crack?
Your joints actually crack as a result of gas.
A gas-filled cavity - known as tribonucleation - forms in the synovial fluid between two joints, creating the popping sound, instead of the common belief that it's from the bubbles being popped, a 2015 study says.
There is no clear link between the act and claims about inflating hands or developing arthritis, according to several studies - but what happens to your bones, exactly?
The effect of cracking joints on your bones
Siobhan, a certified Canadian internal medicine and rheumatology specialist, is known on social media as 'Violin MD'.
She spoke of how a 1970s study determined that the cracking noise was caused by the bubbles between your joints popping.
However, it seems this is no longer the case, as a 2015 study looking at pulling someone's finger while in an MRI machine revealed that an air bubble forms, staying there long after the cracking sound.
What did the study find?
The medical expert explained: "Scientists concluded that the sound must be coming from an air bubble forming rapidly rather than collapsing as it was previously believed.
"Here's how that would actually work - as you're pulling two bones apart again you're causing negative pressure but synovial fluid is really thick and it would resist being pulled apart. If you pull hard enough then all of a sudden the fluid would separate, turning into a bubble and causing that cracking sound as it pulls apart."
Siobhan said that this theory was disputed by some scientists, as one even claimed the MRI machine takes snaps too slowly, taking a picture every 310 milliseconds, while these events could take less than five milliseconds.
She added: "Here's what we can take away from all of this research, when you pull on your finger you're causing negative pressure and that causes a bubble to form at around the same time that you hear a cracking sound, then perhaps the bubble rapidly forms and immediately partially collapses like the mathematical model predicted."
"I'm really shocked that we don't have a definitive answer," she said of the studies, as many people are guilty of cracking their knuckles.
Siobhan also confirmed that the habit isn't 'bad' for you as no damage is done to the joints, as one doctor from California claimed to crack his left knuckles twice a day for 50 years while never cracking his right hand, with an X-ray showing no arthritis in either.
Joshua Nair