If you’re a knuckle-cracker, you’re going to like this story.
You’ve no doubt heard – from your mom, and the people that you annoy when you make that horrible cracking sound – that you should stop popping your knuckles before you get arthritis or some other horrible joint disease.
Fret not, noisy friends. According to a recent study, knuckle cracking is beneficial.
Inside The Crack
Our story starts with Dr. Robert Szabo, a hand surgeon at the UC Davis Medical Center and former president of the American Society for Surgery of the Hand. Dr. Szabo has a nurse on staff who drives him crazy because she cracks her knuckles incessantly. So he told her that she should knock it off, because she was damaging her joints.
Nurse Johnson issued a challenge: “Prove that it’s bad.”
Much to his surprise, Dr. Szabo was unable to find any scientific studies that demonstrated any harm associated with knuckle cracking. So you can image his glee when, sometime later, his colleague, Dr. Robert Boutin, a radiologist at UC Davis, asked Szabo to participate in a knuckle-cracking study. Here he would find the evidence he needed to make nurse Johnson kick her habit.
Boutin and Szabo gathered together a bunch of knuckle-crackers (including Nurse Johnson) and asked them to methodically crack away under an ultrasound machine so they could see what happens when knuckles are cracked. Some participants, who ranged in age from 18 to 63, yanked on their fingers, others flexed or bent them back to create a satisfying crack.
The doctors then examined the knuckles pre- and post-crack. To validate their findings, they examined the knuckles of a group of non-crackers too.
The results? The knuckle-crackers didn’t have any hand problems. No joint hand swelling, no lessening of their grip strength. In fact, after someone cracked a knuckle, that knuckle demonstrated an increased range of motion compared with knuckles that hadn’t been cracked.
The study was presented in December at a meeting of the Radiological Society of North America. It has not been published in a peer-reviewed journal as yet.
Boom Go the Knuckles
Boutin and Szabo looked at the ultrasounds of 400 knuckles being cracked, and noted a very interesting thing. When a knuckle cracked, ultrasound revealed that there was a distinctive and sudden flash – like a tiny fireworks explosion – in the joint.
Apparently, cracking the knuckles creates negative pressure, which frees the gas contained in joint fluid. The bright flash is a gas bubble forming. The negative pressure created by cracking also frees up the joint itself, temporarily increasing its range of motion.
Does that mean we should all take up knuckle cracking? Nope. But what the study seems to indicate is that the habit won’t cause any harm. But bear in mind that these new findings directly contradict a large and often-quoted 1990 study that associated knuckle cracking with hand swelling and lessened grip strength. Boutin and Szabo are very clear on the fact that the jury is still out on knuckle-cracking, especially since they looked only at the short-term effects of cracking. A bigger, extended study might contradict their findings.
But meanwhile, Dr. Szabo will have to put up with the sound of Nurse Johnson’s knuckle cracking.
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