In the first ever study of its kind, researchers were able to simulatenously record audio and visual evidence of a knuckle cracking.
There were 17 women and 23 men between 18 and 63 years old all examined using ultrasound imaging as they attempted to crack their knuckles.
“It's extremely common for joints to crack, pop and snap. We were interested in pursuing this study because there's a raging debate about whether the knuckle-cracking sound results from a bubble popping in the joint or from a bubble being created in the joint,” said Robert Boutin, Professor of radiology at the University of California.
Orthopaedists who didn’t know the participants’ knuckle-cracking history then evaluated each person for grip strength and range of motion both before and after the ultrasound.
Using a transducer, a sonographer recorded video images of the participants cracking their knuckles.
“What we saw was a bright flash on ultrasound, like a firework exploding in the joint. It was quite an unexpected finding,” continued Professor Boutin.
According to Professor Boutin, there had been several theories over the years about what happens in a joint when it cracks. But now they’re confident that the bright flash and the cracking sound are related to the pressures associated with a gas bubble in the joint.
Despite making a huge leap in research, further tests are needed to determine whether the cracking sound or the flash of light come first.
Physical examinations show no immediate pain or swelling when knuckle-cracking and there is no difference in laxity or grip strength following a knuckle crack.
“We found that there was no immediate disability in the knuckle crackers in our study, although further research will need to be done to assess any long-term hazard - or benefit - of knuckle cracking,” Professer Boutin concluded.
Try and explain that to mum next time she tells you off about it.
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