Since you were a kid, you've likely heard warnings that popping your knuckles will destroy your joints, or at least prevent you from being a brain surgeon like your father wanted. But for the longest time, no one really knew why joints cracked, or whether doing so really caused arthritis or other joint problems down the road.
Thankfully, there's a researcher for every question: scientists decided to attempt cracking the code once and for all to see if there is any credence to this old wives' tale. There's good news to be had -- well, for knuckle crackers, anyway.
It looks like a firework in your joint
Dr. Robert D. Boutin, professor of radiology at the University of California, Davis Health System, looked into the joints -- literally -- to find out what causes a knuckle to crack, and if doing so produces any disastrous results. He and a team of researchers studied the goings on inside the knuckle where the fingers meet the hand (aka the metacarpophalangeal joint for you science-y types) because, really, it's weird that you can move a joint and a loud sound emerges from it.
Like every major health discovery throughout history, this one was inspired by childlike wonder. "My 12-year-old daughter noticed kids at school were cracking their knuckles," he explained. "She wanted to know, 'What causes that peculiar sound, and is it bad for you?'"
Boutin's study involved 40 healthy adult volunteers who agreed to crack their knuckles while undergoing ultrasound on the joint. Sounds like a pretty fun gig! Thirty of these volunteers were habitual poppers; the others were not. The subjects were evaluated for grip strength, range of motion, and how loose the joints are both prior to and after the pop, and the scans were evaluated to find out what the hell goes on in there when the crack happens.
Turns out, the joints "light up" when you pop them. No, really -- the researchers described them as "fireworks." Basically, there is a change in pressure when the joint is cracked, which results in a gas bubble creating a mini explosion of sorts, which shows up as a streak of light during sonography.
So does this mean I'm exploding my joints?
Knuckle cracking has been studied before, and while researchers found that it hasn't been shown to cause arthritis (yay), one of the larger studies done on the topic indicated that it seemed to be associated with swelling and decreased grip strength. This isn't something that you really want to experience, right? No. No, you do not.
In this study, though, researchers who weren't aware of the volunteers' knuckle-cracking history didn't detect anything bad happening to the volunteers immediately after the crack, which means there was no difference in strength and there wasn't any swelling. The major change uncovered was that the joints moved a little better after popping, and those of us who do pop their knuckles can attest that it can feel pretty badass and relieving.
And as far as whether everyone should hop on the knuckle-cracking train based on this study? Maybe, maybe not. "There is so much to learn about common, everyday habits that we may take for granted," says Dr. Boutin. "We just don’t have the data to give definitive answers at this time." In other words, there were no immediate issues, but long-term research needs to be done before doctors will give a definitive "yay" or "nay." Pesky doctors, with their need for evidence.
While Dr. Boutin says that maybe there is a segment of the population that shouldn't crack their knuckles, there is no evidence-based medicine that demonstrates this one way or another. But he does say that a little common sense goes a long way. "If something hurts, don't do it!" he advises. Now, if only everyone can keep that in mind before they tell someone to hold their beer and "watch this trick."
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