Why Do People Crack Their Knuckles and Is It a Bad Thing?

Has anyone ever told you that if you keep cracking your knuckles they’ll get big and deformed or you’ll give yourself arthritis? Maybe they really thought that … or maybe the popping noise was just annoying the hell out of them and they wanted you to knock it off already.

Research presented at a recent annual meeting of the Radiological Society of North America (RSNA) examined the mystery of knuckle cracking. The doctors used ultrasound to observe knuckle cracking action in real time.

What actually causes the sound that irritates so many people?

The study included 40 adults, 10 who were not knuckle crackers, and 30 habitual knuckle crackers, some of whom reported cracking up to 20 times a day for decades.

The ultrasound images showed bright flashes of light exploding in the joints as they cracked. Researchers believe the sound and bright flash has to do with changes in pressure associated with gas bubbles within the joints.

So, does cracking harm your joints?

On physical examination, researchers found no swelling, pain, or any kind of disability in recently cracked knuckles. The researchers say more studies are needed to assess if there’s any long-term hazard, or even some benefit of cracking your knuckles.

As for which came first, the bubble or the crack, that’s a mystery yet unsolved.

“It’s extremely common for joints to crack, pop and snap,” said Robert D. Boutin, MD, professor of radiology at University of California, Davis (UC Davis) Health System. “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,” he said in an RSNA press release.

Matt Likins, PT, MPT, OCS, told Care2 there are more studies showing there are no ill effects from knuckle cracking, and it matches his personal experience. He’s been cracking his knuckles for over 30 years. “We know that ‘popping’ a joint releases endorphins that provide temporary pain reduction (that’s why chiros stay so popular). So aside from possibly annoying those around you, keep on popping!”

Ken Zehnder, MD, Mid County Orthopaedic Surgery & Sports Medicine, believes it’s just an annoying habit of some nervous people. “I don’t think it causes any harm to your hands if done in moderation.”

So there you have it. You’re probably not causing damage to your knuckles, although you might be causing a few people to cringe. Then again, maybe that’s part of the appeal.

Comedian and molecular biologist Adam Ruben is co-host of the Science Channel’s Outrageous Acts of Science. The self-proclaimed habitual knuckle cracker says he’s not sure why he cracks his knuckles all the time, but he doesn’t stop at his knuckles.

“I crack my toes, neck, back, knees, etc. sometimes, too,” he said. “My wife hates it. She has now accepted that she can’t stop me, but she’s gotten me to agree not to crack my knuckles against my chin which, for some reason, works really well.” He’s not particularly worried about detrimental effects.

Why do people crack their knuckles?

I’m not a knuckle cracker. I don’t even know how to do it, although my ankles and elbows tend to crack with no assistance from me. So I reached out to a few knuckle crackers to find out why they do it. I received some interesting responses:

To be like Bruce Lee

I sit at my computer most of the day. I also probably crack my knuckles once an hour or so. Strangely enough, I think I can trace my habit all the way back to when I was a kid watching Bruce Lee movies. When he was preparing for a fight, he’d often go through a joint cracking routine. I started doing it because as a kid, well, who didn’t want to be like Bruce Lee?

As I got older, I learned to play guitar. All of the rigid finger positions for playing chords always made my hands sore. So I would crack my knuckles in between songs to try and loosen things up. Combine that with running a website and typing all day, and I don’t think I will ever stop.

As far as I can remember, no doctor has ever told me to quit. My mom used to, but I always ignored her advice. Sometimes I do wonder though if my sore hands can be attributed to all that finger popping…

- Chris Brantner, a.k.a. Mr. Cable Cutter, cutcabletoday.com

It relieves stiffness and just plain feels good

This started in my early 20s, when I was doing a bunch of hand exercises for karate, and I discovered that my hands felt better and my fingers could move a little smoother when I did so. This habit has continued ever since (almost 60 now). It is essential in the morning when I get up to write: without cracking my knuckles, my fingers move stiffly. I will crack my knuckles several times a day without thinking about it.

My wife is one of those people who twitches when they hear knuckles being cracked, so I do get annoyed comments occasionally. Other than that, I’ve not had any significant problems with arthritis or anything else because of this.

- John Hedtke, consultant, author, contract writer

Nervous habit…and for the reaction

I’m a committed knuckle cracker, and have been since my teenage years. It started as a nervous habit; cracking my knuckles before picking up a pen in an exam, or before lifting a heavy weight in the gym. I’m quite a big guy and spend a lot of time lifting weights. I think the knuckle cracking adds to the image of being “physically capable” although most people probably just find it gross. My girlfriend likes to crack my fingers for me when we’re relaxing around the house, which is delightfully weird of her!

The reactions of people around me (mostly horror or cringing disgust) only encouraged me to crack more theatrically; I can now crack the joints in my neck on command!

- James Armstrong, owner of cavemanstore.co.uk

To calm anxiety, and it’s contagious, too

I’ve been doing it since I can remember, and I think it started as a reaction to anxiety. Any time I get stressed out I do it, however when I read your query it made me want to do it, too. It also feels good, like popping bubble foil. It’s got a calming effect on me for some reason. Maybe it’s the release and the “crack” sound that’s comforting. I don’t know how to explain it, but it’s just one of those things you do.

My fiance is also a habitual cracker just like me, and we don’t see anything wrong with it. We don’t really think about it, but when I do it he has the urge to and vice versa.

Many of my friends have told me not to do it or I’m going to get huge knuckles or get sick later in life where I can’t move my fingers properly. But I don’t believe that to be true. None of my doctors have ever told me to stop, when I asked my GP if it’s harmful he said there is no research to suggest that it is a hazard.

- Vivi, fashion blogger

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Photo Credit: Jaysin Trevino


Kelly S
Past Member about a year ago


Richard A.
Richard A2 years ago

When I was a child I was told that knuckle cracking would cause swollen knuckles and joint pain later in life.

Siyus Copetallus
Siyus Copetallus2 years ago

Thank you for sharing.

Peggy B.
Peggy B3 years ago

LOL. I don't do it, but it doesn't annoy me when someone does it. To each his own.

Pamela Dubsky
Pamela Dubsky3 years ago

My husband hates when I do this, but it's a habit!

Sarah Hill
Sarah Hill3 years ago


Kathryn Irby
Past Member 3 years ago

Definitely a nervous habit!! Thanks for posting.

Kathryn Irby
Past Member 3 years ago

My aunt used to always do that; think it was a nervous habit. Thanks.

Jim Ven
Jim Ven3 years ago

thanks for the article.

Carole R.
Carole R3 years ago

I don't do it and I hate to hear it done. Wonder how much this study cost?