We have all experienced the satisfying feeling of cracking knuckles; it’s like your life is a bit more together after you hear them knuckles pop, right? However, the source of the “cracking” sound was a mystery until today, when researchers finally found the little gas bubble between the bones that makes the sound.
Incidentally, researchers not only cracked open the mystery, but also found an interesting flash of bright light occurring 10 milliseconds after the sound. By using an ultrasound imaging, the researchers from the University of California, discovered a surprising likeness to tiny fireworks that pop in between the flexed joints.
For the study, the research team of Robert Boutin, a radiologist, enrolled 40 people – 17 women and 23 men – for an experiment; the participants were 18 to 63 years old. Their task was simple: just crack their knuckles simultaneously, an activity carefully recorded via ultrasound imaging.
The study revealed 10 of the participants never cracked their knuckles, while 30 reported doing it often. Among the participants who cracked their knuckles – with a frequency of about 20 times daily for years – the researchers found only healthy joints. The results are proof that provided people don’t have preexistent joint problems, knuckle-cracking doesn’t seem to cause any damage.
Boutin explained that “no immediate disability in the knuckle crackers” could be found during the study, although he recommended further research to be done before knuckle cracking could be regarded as either hazardous or beneficial.
Over the years, several theories have floated around trying to explain what happens when people crack their knuckles, but none could be scientifically proven. Apart from the unanimous opinion that it gives a satisfying release, researchers were stumped.
Boutin’s team said a little gas bubble located between the joints could be responsible for the short bright light and cracking sound, which changes pressure when we do the cracking motion. According to Dr. William Palmer from the Massachusetts General Hospital, this gas bubble acts as joints’ lubrication.
Dr. Palmers, who is also the chief of musculoskeletal imaging at Massachusetts General Hospital, explained the motion of cracking stretching the fingers results in a negative pressure which yanks the gas out from between the joints, breaking the seal.
Bouting added that more tiny bubbles could also merge into one large bubble, which would explain why you can’t crack your knuckles more than once in a short period of time. The team found no evidence that regular knuckle crackers suffer from swelling or decrease in grip strength.
Image Source: OMG Facts