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Can make-up harm your eyes? An interview with an optometrist
by Natalie Hemengül
Fact or fiction: does cracking your knuckles destroy your joints?
28.1.2026
Translation: Patrik Stainbrook
You've probably been warned that cracking your fingers is unhealthy. But what actually happens if you crack your fingers? And do you have to fear serious consequences?
You’re sitting in a meeting, a lecture or watching a movie together, and suddenly the person next to you starts cracking their fingers. The sound is somehow magical, but annoying too. If you’re addicted to knuckle-cracking yourself, you’re probably familiar with those reproachful looks from people around you. Or maybe you still hear your mother say: «Stop that! You’re hurting yourself.» The good news first: no, you aren’t. And here’s the annoying bit for those around you: you can carry on doing it, it won’t do any harm.
What makes the cracking noise?
Admittedly, cracking your knuckles sounds more worrying than healthy. However, you don’t damage your bones – the noise is instead produced by small air bubbles. Here’s how: there’s a liquid between your finger joints – synovial fluid. It’s basically lubricating oil for your joints. Gases such as nitrogen and carbon dioxide are dissolved in the liquid.
Whenever you pull on your finger or overstretch it, the gap between the joints widens, suddenly reducing the pressure on your synovial fluid. If the pressure drops, the liquid can no longer contain its gases. They bubble out – like opening a bottle of champagne.
Source: Kawchuk GN et al. (2015), PLOS ONE
The cracking sound doesn’t come from you dislocating your joint or breaking your bones. It’s just the sound of tiny gas bubbles forming. Canadian researchers proved this in 2015 with high-resolution MRI videos – filmed live while participants cracked their knuckles.
After a crack, the small cavity between joints remains visible. Only after 15 to 20 minutes do the gases dissolve back into the liquid – your fingers are ready for the next round. It’s why you can’t immediately crack the same finger again.
Does cracking break anything?
I’ve already spoiled it, but now I’ll go into more detail: all those well-meant warnings were unnecessary. Cracking doesn’t harm your joints.
Regardless, one person who wanted to know exactly what happens to them was American allergist Donald Unger. In a wild self-experiment, he cracked his fingers several times a day for over 60 years – but only on one hand. He left the other hand completely untouched. After six decades, X-rays of both hands revealed no differences. No arthritis, no arthrosis. Nothing.
However, this isn’t the only anecdote. There are scientific studies on the subject too. One study tracked over 200 senior citizens, comparing finger crackers with non-crackers. Again, there were no differences between the groups.
Source: Shutterstock
A more recent study from 2017 also looked at whether you can see immediate differences after cracking – swelling, loss of strength, any acute damage. Again, nothing. On the contrary: people who crack even had slightly better mobility in their fingers.
When to stop cracking
But before you start cracking like crazy and drive those around you mad, a few small caveats: cracking should never feel painful. Pain is always a warning signal from your body. There may be something wrong with your joints in such cases – a strain, inflammation or other injury. Swelling isn’t a good sign either. This could also indicate inflammation. If your finger cracking becomes compulsive, it could be a sign of stress or anxiety. In these cases, it’s always best to seek medical advice.
The psychological element
By the way, plenty of people say that cracking their fingers feels relaxing. And this isn’t just made up. Whenever you stretch your joints, you stimulate nerve endings, which send signals to your brain. Cracking itself is a small sensory event – your brain likes that. And if you crack regularly, your brain associates this with relaxation.
From a medical point of view, there’s absolutely nothing standing in the way of your finger cracking habit. As far as the patience of your roommates and family are concerned, you may have to find other solutions.
Header image: Bricolage/Shutterstock
Anna Sandner
Senior Editor
Anna.Sandner@galaxus.deScience editor and biologist. I love animals and am fascinated by plants, their abilities and everything you can do with them. That's why my favourite place is always the outdoors - somewhere in nature, preferably in my wild garden.
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