This Is What Really Happens To Your Knuckles When You Crack Them

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Many people just can’t resist cracking their knuckles, no matter how many shudders and screeches of repulsion they cause.

Whether they find it satisfying or just enjoy creeping out their mates, the gruesome trait is arguably right up there with the big no-no’s of public nose-picking or peeling back your eyelids.

But yet, it’s so much more common, with most of us guilty of releasing some pent up tension in this way at one time or another.

But what happens to your knuckles when you crack them? And is this truly the grim road to arthritis-ville your mum always warned you about?

According to Harvard Health Publishing, this bone popping activity probably doesn’t increase the likelihood of arthritis.

This is reportedly according to several studies which compared rates of hand arthritis those who cracked on the regular, and those who refrained.

One researcher actually studied himself; habitually popping the joints in his left knuckle while leaving the right one be. This experiment carried on doggedly for six decades, and revealed no increased prevalence of arthritis in his left ‘popping’ hand.

According to Harvard Health Publishing:

The “pop” of a cracked knuckle is caused by bubbles bursting in the synovial fluid — the fluid that helps lubricate joints.

The bubbles pop when you pull the bones apart, either by stretching the fingers or bending them backward, creating negative pressure. One study’s authors compared the sudden, vibratory energy produced during knuckle cracking to “the forces responsible for the destruction of hydraulic blades and ship propellers.”

However, even if you could crack all day long without fear of arthritis, this really wouldn’t be a good idea. Not least because you might begin to alienate everyone you know.

Those with a chronic cracking habit may run the risk of swollen hands and weakened grip, according to some studies.

Furthermore, at least two reports of injuries suffered due to knuckle-cracking. Best to swap your poor knuckles for a stress ball or fidget spinner if you ask me.

According to the conclusions of one study published in the Annals of the Rheumatic Diseases:

Although habitual knuckle cracking does not relate to osteoarthritis of the hand, it may relate to decreased hand function.

Therefore, habitual knuckle cracking should be discouraged.

But what actually causes that audible cracking or popping noise which knuckle crackers so eagerly strive for?

Back in 2015, University of Alberta scientists published imaging based research which found how the distinctive ‘popping’ noise is due to air bubble formation of in the synovial fluid surrounding the joints.

Speaking with The Washington Post, Professor Robert D. Boutin discussed the study; which put the cracking knuckles of 40 patients under an ultrasound machine.

According to Professor Boutin, the team found ‘ultrasonic evidence’ of how pressure changes associated with joint fluid bubbles cause knuckle cracks:

What we saw was a bright flash on ultrasound, like a firework exploding in the joint, It was quite an unexpected finding. […]

I will tell you that we consistently saw the bright ‘flash’ in the joint only after we heard the audible crack.

Interestingly, there were 30 habitual knuckle crackers in Professor Boutin’s experiment, and there were no obvious signs to show their gross habit had negatively affected them.

Best not to inflict it on your friends though…

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Julia Banim

Jules studied English Literature with Creative Writing at Lancaster University before earning her masters in International Relations at Leiden University in The Netherlands (Hoi!). She then trained as a journalist through News Associates in Manchester. Jules has previously worked as a mental health blogger, copywriter and freelancer for various publications.