If you're one of the millions of knuckle-crackers out there, you've probably heard time and again that this habit will cause arthritis. But what does the science say?
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Here's the real deal on what happens when you give your joints a snap, crackle and pop.
Why Knuckles Crack
Somewhere between 25 and 45 percent of people crack their knuckles, according to an April 2017 study in Clinical Orthopaedics and Related Research.
"Some find knuckle cracking pleasurable because the movement of tendons and ligaments around the joint can relieve tension," rheumatologist Magdalena Cadet, MD, assistant professor of medicine at New York University Grossman School of Medicine, tells LIVESTRONG.com. "Others enjoy the soothing popping sound, and it can provide a distraction when you are stressed."
But have you ever wondered what's causing your joints to make so much noise?
"The knuckles are protected by a capsule containing synovial fluid, which contains nutrients and also lubricates the joints," Dr. Cadet says. "When one cracks the knuckles by stretching, bending or twisting the fingers, negative pressure may cause a variety of gases, including nitrogen or carbon dioxide, to be temporarily pulled into the joints."
These gases release bubbles that create a popping sound when they collapse, per a March 2018 study in Nature.
"You might also hear cracking caused by the movement of tendons and ligaments around the joint," Dr. Cadet says. "Researchers theorize that once an individual cracks their knuckles, it may take up to half an hour before the knuckles can be cracked again, due to the time that it takes for the gases to re-dissolve into the synovial joint fluid."
That's why you can't crack the same knuckle twice in a row.
As for people who aren't able to crack at all: "There is a theory that some individuals have large spacing between the knuckles, which makes them unable to perform this maneuver," Dr. Cadet says.
These folks may be lucky, because knuckle-popping can become addictive.
"Repetitive cracking can become a habit over time as an individual begins to do it subconsciously," Dr. Cadet says.
Can Cracking Your Knuckles Cause Arthritis?
Chalk this one up to an old wives' tale. Knuckle cracking is not a risk factor in hand arthritis, confirmed a March 2011 study in the Journal of the American Board of Family Medicine.
In one of the more unusual pieces of research exploring the relationship between knuckle cracking and arthritis, published in a May 1998 case report in Arthritis Rheumatology, a California doctor decided to experiment on himself. For decades, he cracked the knuckles of only one hand. After a lifetime of this behavior, he took X-rays of both hands and found no difference in arthritis between the two.
Are There Other Possible Side Effects?
"Although many respected medical centers seem to believe that habitual joint cracking probably won't raise the risk for arthritis, there may be reasons to avoid this habit," Dr. Cadet says, pointing to the largest study to date on the matter: a 1990 study in the Annals of Rheumatic Diseases, which found that knuckle-crackers had weakened handgrip strength and more hand swelling.
Plus, a February 1999 report in the American Journal of Orthopedics described two injuries to the tendon and ligament caused by forceful knuckle-cracking.
But newer research hasn't turned up any troubling issues.
In a small February 2017 study in Hand Surgery & Rehabilitation, comparing 35 knuckle-crackers to 35 noncrackers, those who cracked did not have a weakened grip, although they did have thicker cartilage.
The 2017 Clinical Orthopaedics and Related Research study looked at 400 joints in 40 people and confirmed that people who cracked their knuckles did not have increased swelling, weakness or joint laxity, or diminished physical function. In fact, study participants had a slightly greater range of motion in joints that cracked.
3 Red Flags: Pain, Swelling or Decreased Motion
Does it hurt when you crack your knuckles? Do your hands look puffy? Have you noticed a limited range of motion in your fingers?
Don't ignore these worrisome symptoms. "Seek medical attention from a physician to investigate an underlying joint condition," Dr. Cadet says.
One possible culprit is crepitus.
"Crepitus is a term used to describe creaking, cracking or popping joints due to arthritis or injury," says John-Paul Rue, MD, orthopedic surgeon at Mercy Medical Center in Baltimore. "As opposed to the intentional cracking of a knuckle, crepitus happens even with passive movement."
For example, if you had crepitus of the fingers, you would hear a crunching or clicking noise when you moved them. And if you placed your left hand on top of your right fingers and wiggled them, you would perceive a mechanical grinding sensation.
"It's as if two 80-grit pieces of sandpaper were rubbing past each other," Dr. Rue says. "You would feel pain, as opposed to the relief of a cracked knuckle."
Arthritis is a common cause of crepitus.
"Osteoarthritis of the fingers is a result of wear and tear to the joints due to age or repetitive motion," Dr. Rue says. "It can also occur after a severe hand injury with damage to the cartilage."
Cartilage is the smooth tissue at the ends of our bones that provides a super slick, lubricated surface for joints to glide easily past each other. If your cartilage is ground down or impaired, there's more friction when your joints move, which can lead to crepitus.
Inflammation of the tissues due to rheumatoid arthritis (an autoimmune disease) or tendonitis (where the tendon swells due to overuse or injury) can also precipitate crepitus.
"Inflammation breaks down the glossy surface of the joint," Dr. Rue says. "It becomes irritated and abnormally thickened, with a friable consistency."
Your doctor may give you an exam or X-ray to see if there's anything structurally wrong with the surface of your joints and bone.
But just to be crystal clear: Knuckle cracking isn't to blame for crepitus.
So, How Bad Is It Really to Crack Your Knuckles?
Aside from the fact that you'll bug the people around you, the science to date indicates you're in the clear. "Crack away!" Dr. Rue says.
Still, Dr. Cadet urges caution: "Although there is no concrete evidence that habitual joint cracking raises your risk for arthritis or is hurtful, I would suggest finding other ways to relieve stress and tension."
3 Tips to Quit Cracking
Even if it's not bad for your health, it is an annoying habit. Here are a few things you can do instead:
1. Keep Stress in Check
If you're a stress-cracker, look for other ways to keep your anxiety in check, such as deep breathing, exercise or meditation.
2. Replace Cracking With Stretching
Stretching your fingers and forearms may reduce the urge to crack.
Try this routine:
- Extend your arms, open your palms with your fingers pointed up in a "stop" motion and use your other hand to gently pull your digits back toward your body.
- Then, with your arms still outstretched, bend your wrists so your fingers are pointed toward the ground and press on the back of your palm.
- Finally, close both hands in a fist and then open them, stretching and spreading your fingers as wide as you can.
3. Keep Your Hands Busy
Squeeze a stress ball or play with a fidget spinner so you physically can't crack your knuckles.
Is This an Emergency?
- Johns Hopkins Arthritis Center: "Knuckle Cracking Q & A"
- Journal of the American Board of Family Medicine: "Knuckle Cracking and Hand Osteoarthritis"
- Arthritis Rheumatology: "Does knuckle cracking lead to arthritis of the fingers?"
- Annals of Rheumatic Diseases: "Effect of habitual knuckle cracking on hand function"
- American Journal of Orthopedics: "Consequences of knuckle cracking: a report of two acute injuries"
- Hand Surgery & Rehabilitation: "Effects of habitual knuckle cracking on metacarpal cartilage thickness and grip strength"
- Clinical Orthopaedics and Related Research: "“Knuckle Cracking”: Can Blinded Observers Detect Changes with Physical Examination and Sonography?"