Does Cracking Knuckles Cause Arthritis? What the Evidence Says

Does cracking knuckles cause arthritis?

Does cracking knuckles cause arthritis? The research says no. Harvard Health and Cleveland Clinic both conclude that the habit is not linked to arthritis, and studies of hundreds of people back them up. The warning you heard as a kid, that you will ruin your hands, is one of the most tested and least supported health myths around.

That does not mean the person complaining has no case. The sound can be genuinely annoying, and forceful cracking can occasionally injure a finger. But if the argument is specifically about arthritis, the cracker wins.

What makes the cracking sound?

Your finger joints are cushioned by synovial fluid, which contains dissolved gas. When you pull or bend a knuckle, the space inside the joint widens and the pressure drops. The classic explanation is that a gas bubble bursts; a 2015 MRI study, described by Cleveland Clinic, instead caught a gas-filled cavity forming at the moment of the crack. Researchers still debate the exact mechanism.

Either way, the noise is gas, not bone. Harvard Health notes that you can't crack the same knuckle again right away because the gas needs time to build back up. That is why a knuckle you just cracked won't pop again for a while.

The verdict

What it sounds like

The doctor who cracked one hand for 60 years

The most famous evidence is an experiment of one. Donald Unger, a California physician, cracked the knuckles of his left hand every day for more than 60 years and never cracked his right hand, so the right could serve as a comparison. He reported in the journal Arthritis and Rheumatism in 1998 that he found no difference in arthritis between his hands, and the work earned him the 2009 Ig Nobel Prize in Medicine.

One person is not proof, and it would be an anecdotal argument if it were the only evidence. It is not. Larger studies point the same way.

What larger studies found

Three studies are worth knowing if this argument comes up at dinner:

1990, 300 patients

Researchers compared 74 habitual knuckle crackers with 226 people who did not crack, all aged 45 or older. Arthritis of the hand was no more common in either group. The crackers were more likely to have hand swelling and lower grip strength, but they were also more likely to do manual labor, bite their nails, smoke and drink, which muddies the picture.

2011, 215 adults aged 50 to 89

A study using hand X-rays found osteoarthritis in 18.1% of knuckle crackers and 21.5% of non-crackers, a difference that was not statistically significant. How long or how often people had cracked made no difference either.

2017, 40 adults

Researchers examined 30 habitual crackers and 10 non-crackers with ultrasound and blinded physical exams. They found no differences in hand function scores or grip strength, no swelling, and slightly more range of motion right after a crack.

Is cracking your knuckles bad for you in any way?

Mostly no. Harvard Health says knuckle cracking is unlikely to cause harm, though it mentions rare reports of dislocations and tendon injuries from overly forceful cracking. A Cleveland Clinic sports medicine doctor gives the same caution: pushing too hard or pulling in the wrong direction could dislocate a knuckle or injure a ligament.

The grip strength worry comes from the 1990 study, and the 2017 study did not find it. So the honest summary is that ordinary cracking looks harmless, and forcing a joint that won't crack is a bad idea.

When to see a doctor

Cleveland Clinic's advice is simple: cracking should not hurt. As long as you have no pain or swelling, it is probably fine. See a healthcare provider if you notice:

• Pain when you crack a joint or afterward.
• Swelling in a finger or knuckle.
• A finger that looks crooked or out of place.
• Noises in your knees or other joints that come with pain or swelling. Harvard Health says joint sounds without those symptoms are probably nothing to worry about.

The ruling

No, cracking your knuckles does not cause arthritis. The person who cracks wins the health argument, and the person who hates the sound is free to keep complaining about the noise, which is a fair point about living together rather than a medical one.

"My grandfather cracked his knuckles and got arthritis" is a post hoc argument: one case can't show the habit caused it, especially when larger studies find no link. If you want someone to stop, say what actually bothers you with an I statement ("the sound gets to me during movies") instead of a health scare. Still arguing? Run it past the argument judge.