The Knuckle-Cracking Myth Solved

Snap, crackle, pop! It’s that sound that will have your mother saying, “Stop doing that! You’re going to get arthritis!” But will it? The myth and stories around knuckle-cracking have been passed on for years, often with differing views supported by sloppy evidence. However, recent studies are coming out to support the claim that knuckle-cracking is not harmful and will not cause arthritis. But first, what causes your knuckles to crack?

Researchers at U.C. Davis looked at 400 knuckles through ultrasound to investigate the mechanism of the cracking. What they found when a knuckle was cracked was a distinctive and sudden flash in the joint. Their insight on the process: when a knuckle is cracked, the joint space widens as the two surfaces of the joint are pulled apart. This widened space lowers the pressure in the joint. The gas that’s dissolved in the fluid in your joints are liberated under this negative pressure. A gas bubble forms, which under the ultrasound is the bright flash, and audibly, is the “crack”. Lowering the pressure allows more laxity, which is why one may have increased range of motion after cracking a joint. The study also showed that under physical examinations none of the participants had hand pain, swelling, or disability in knuckles that were cracked.

Even with the evidence, mythology that has been passed down generations is hard to break. A study in 1990 found that knuckle-crackers were more likely to have hand swelling and lower grip strength.  However, the study was not without flaws, and more current research is coming out to support what the investigators at U.C. Davis suggested: cracking your knuckles is not harmful. If it is painful when you crack your knuckles, then consult with a hand therapist or general practitioner.

So, if you need a rebuttal to give to your family members or co-workers the next time they scold you for cracking your knuckles, give them this: it’s just gas.




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