A lot of people just can’t resist the temptation to crack their knuckles, no matter how many screeches or shudders of revulsion they might evoke.
Whether they find it oddly satisfying or just enjoy freaking out their friends, the strangely popular habit is arguably right up there with the big no-no’s of public nose-picking or passing gas in mixed company.
And yet, it’s such a common occurence, with most of us guilty of popping our fingers at one time or another.
“Many believe that the cracking sound is the bones realigning, which couldn’t be further from the truth,” said New York City–based physical therapist Scott Weiss, D.P.T. “It actually has it do with the fluid inside the joints and the gases that are dissolved in those fluids.”
As for why the sound is so loud, science still isn’t totally sure. However, researchers do know why you can’t crack the same joint over and over again.
“The gases take about 20 minutes to fully dissolve back into the fluid,” said San Diego–based chiropractor Ryan Curda, D.C. “That’s the refractory period—the amount of time that needs to pass until you can get cracking again.”
Aside from being a conspicuous habit, cracking one’s knuckles actually releases several pounds of pressure from the joints.
As you use your hands throughout the day and the muscles tighten up, the joints end up feeling tense as well.
“Cracking the knuckles gives your fingers and joints a stretch to relieve that pressure buildup,” says Curda.
In other words, people crack their knuckles for the same reasons they might take a nice, big stretch after sitting for a long time.
But what happens to your knuckles when you crack them? And is this habit truly the horrendous road to arthritis-town your mother always warned you about?
There Are Different Theories About What Causes the ‘Pop’
Some doctors have erroneously proposed that the cracking sound is the result of tendons snapping into place over joints.
The sound of a joint cracking is often confused with the similar sound made by stiff tendons sliding between muscles or over bony outcrops.
Tendons keep muscles attached to bones while ligaments connect bones to other bones.
Some doctors believe that tendons can make a popping noise when they quickly snap over a joint.
Ligaments can also make popping noises when they tighten while the joint is moving.
When a joint moves, the tendon changes position and can cause a sudden snap as it returns to its original location.
These noises are often heard in the knee and ankle joints when standing up from a seated position or when walking up or down a flight of stairs.
But what actually causes that audible pop which knuckle crackers find so satisfying?
Turns Out It’s All About the Pressure Inside the Joint
One popular theory is that when a finger or joint is extended, the pressure inside the finger is lowered and the gases that are present are released in the form of a bubble.
The bubble-collapse theory suggests that popping joints create a vacuum that the gases then fill.
Then, when joints are extended through pulling, there is a sudden and dramatic increase in the surrounding pressure.
This causes a sudden partial or total collapse of these gas bubbles, and this collapse is heard as the popping sound.
But recent research has debunked the bubble-collapse theory on the basis of visual evidence of what happens in the joint when the cracking sound is heard.
By collecting real-time footage using a magnetic resonance imaging machine, one study concluded that joint cracking is related to cavity formation rather than the collapse of gas bubbles.
Apparently, there’s no need for gas bubbles for the sound to occur.
But that’s not all there is to the mystery of the cracking sound. And there’s some really amazing research that’s shedding light on the strange phenomenon…
New Research Shows Cracking Is Actually ‘Ultra-Sonic’
Back in 2015, scientists at the University of Alberta published research that showed how the distinctive popping noise is due to air bubble formation of in the synovial fluid surrounding the joints.
Professor Robert D. Boutin imaged the cracking knuckles of more than 40 patients in an ultrasound machine.
According to the data collected, the team found ultrasonic evidence of how pressure changes associated with joint fluid bubbles cause knuckle cracks.
“What we saw was a bright flash on ultrasound, like a firework exploding in the joint,” he said. “It was quite an unexpected finding. I will tell you that we consistently saw the bright flash in the joint only after we heard the audible crack.”
But whatever the causative mechanism, does cracking your knuckles actually cause arthritis?
Has your nagging mom been right this entire time?
Cracking Your Knuckles Doesn’t Cause Arthritis
According to Harvard Medical School, cracking your knuckles probably doesn’t increase the likelihood of developing arthritis.
This finding is the result of several studies which compared rates of hand arthritis in those who cracked regularly, and those who refrained.
One researcher actually studied himself!
He habitually popped the joints in his left hand while leaving the right one alone. This experiment carried on doggedly for six decades and ultimately revealed no increased prevalence of arthritis in his left, popping hand.
However, even if you could crack all day long without fear of arthritis, this really wouldn’t be a good idea.
There are actually some other health issues that cracking your knuckles can cause…
Popping Your Fingers Can Cause Some Other Health Issues
Those with a chronic cracking habit may run the risk of swollen hands and weakened grip, according to some studies.
Furthermore, there are many reports of injuries suffered during knuckle cracking.
It’s probably best to swap your poor knuckles for a stress ball or fidget spinner if you ask us!
According to the conclusions of one study published in the Annals of the Rheumatic Diseases, habitual knuckle cracking does not cause osteoarthritis of the hand. However, it may relate to decreased hand function.
Therefore, habitual finger popping should be discouraged.
And just maybe your mother was right all along, although for the wrong reasons!
Do you crack your knuckles?