In short
Why knuckle cracking “pops” and whether it causes arthritis; also potential downsides and minor benefits.
Guests
Josh, Chuck, and Jerry (sitting in for Dave), with Chuck leading much of the explanation; they reference researchers and a specific experimenter.
Key claims
The sound comes from synovial fluid joint capsule pressure dropping, forming and popping gas bubbles (not bones grinding). Arthritis risk: experiments (including Dr. Donald Unger’s 60-year left-hand-only cracking with x-rays) show no arthritic difference.
Notable examples
Raymond Broder’s study of 300 knuckle crackers found no arthritis difference but soft-tissue/ligament capsule damage and reduced grip strength; 1990 study (74 crackers) reported lower grip strength and more swelling. Habitual cracking can cause ligament laxity, swelling, and injury; pitchers stretch ligaments repeatedly. Possible benefit: may relieve muscle tension via Golgi tendon organs (“yoga for your knuckles”).
Written by AI. May contain mistakes. Listen to the episode to check what was said.
Chapters
Tap a time to open that second in VOUnderstanding Knuckle Cracking
1:10 to 4:22
Exploring the science behind what happens when you crack your knuckles.
“Are you cracking your knuckles right now?”
Myth Busting: Knuckle Cracking and Arthritis
6:11 to 13:00
Discussing a study on the effects of knuckle cracking over time and its relationship to arthritis.
“Chuck, I know we've talked about this guy before, Dr.”
Transcript
Automatic transcript. May contain errors.0:00Josh Clark:This is an iHeart Podcast. Guaranteed Human. Stuff You Should Know is brought to you by Grainger. Grainger knows that if you're an HVAC technician and a call comes in, you need a partner that helps you find the right product, fast and hassle-free. And you know that when the first problem of the day is a clanking blower motor, there's no need to break a sweat. With Grainger's easy-to-use website and product details, you can be confident that soon you'll have everything humming right along. Call 1-800-GRAINGER, click grainger.com, or just stop by. Grainger, for the ones who get it done.
0:55Josh Clark:Amazon Health AI. Healthcare just got less painful.
1:03Chuck Bryant:Hey, and welcome to The Short Stuff. Josh, Chuck, Jerry sitting in for Dave. So this is Short Stuff. Chuck, I have a question for you. Are you cracking your knuckles right now?
1:15Josh Clark:I am. Did you hear that?
1:17Chuck Bryant:Yeah. That wasn't like a Foley effect?
1:20Josh Clark:No, I was cracking my knuckles. I'm a knuckle cracker. I don't do it. I did it a lot when I was a kid, but I still do it some.
1:29Chuck Bryant:This is what my knuckles sound like when I crack them.
1:38Chuck Bryant:That's it. Yeah, I can't do it again because I have to wait 20 to 30 minutes for the air bubbles to come back and cavitate once more.
1:49Josh Clark:Yeah, well, tell everybody what's going on here. I know there was a lot of, you know, when you're young, everyone was like, it'll give you arthritis and it's your bones grinding together. And that's what cracking your knuckles is. And that can't be good for you.
2:01Chuck Bryant:Yes. If your bones ground together, you would not be able to think of anything else but your bones grinding together because you would be in so much pain that you would know your bones are grinding together. That's not what cracking your knuckles is. It turns out instead it has everything to do with the space and the area around where your bones come together. Your bones don't actually come together.
2:24Josh Clark:That's right. Where there is a joint, that is where two bones meet, but they're separate. And they're held together by ligaments and connective tissues and all that stuff. But there's also some very other key ingredient in there. It's called synovial fluid. It's a thick, clear liquid that kind of encases that area, right? Yeah.
2:45Chuck Bryant:Uh, it's, it's thick. It tastes just like orange crush, surprisingly. And when you, when you pop your knuckle, what you're doing is stretching or bending the, the ligaments and connective tissues and the synovial fluid there too, right? So when you do that, that capsule is what it's called, the connective tissue capsule that includes the synovial fluid. It gets stretched, which increases its volume. And then suddenly the pressure inside the capsule in that cyanovial fluid, it goes down. It decreases in pressure, which means that all these gases that used to just be part of the solution now are part of the problem.
3:23Chuck Bryant:I mean, now turn into bubbles.
3:26Josh Clark:That's right. So they become, you know, they form those bubbles. And if you stretch that joint far enough, like, you know, trying to crack your knuckles, the pressure in the capsule goes so low that it just pops those bubbles. And that's the popping sound that we're hearing.
3:40Chuck Bryant:There you go. not your bones rubbing together. Okay. I want you to go to recess and tell your friends that is not your bones rubbing together.
3:50Josh Clark:Yeah. Uh, and then the cavitation you mentioned earlier, I think before we break, we should just clear that up. You said 20 to 30 minutes. That is how long it takes for that gas to redissolve into that joint fluid. And, uh, cavitation is, is possible again.
4:06Chuck Bryant:Yeah.
4:07Josh Clark:Go watch, watch me cavitate my knuckles. Yeah, exactly.
4:12Chuck Bryant:Oh, I just did one again. Okay, I say we take a little break and come back and talk about how we know that cracking your knuckles doesn't give you arthritis.
4:21Josh Clark:All right, we'll be right back.
4:25Chuck Bryant:All right.
4:40Chuck Bryant:You know, it's hard to believe that the first phone call ever happened over 150 years ago. Just think about that, Chuck.
4:47Josh Clark:Yeah, it was a long time ago. And, you know, I'm Gen X, so I grew up talking on the phone with my friends in high school and stuff. And it was a really fond memory.
4:54Chuck Bryant:And, you know, over all these years and all these phone calls, AT &T has been there, connecting people in meaningful ways. And this is more than a story of technological innovation. It's a story of human connection.
5:06Josh Clark:That's right. Over that 150 years, there's been a lot of connection with people, whether it was me in high school or family connecting with one another long distance or those long distance relationships. And AT &T has been there for it all. Connecting changes everything. AT &T.
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6:13Josh Clark:Wayfair, every style, every home.
6:31Chuck Bryant:Chuck, I know we've talked about this guy before, Dr. Donald Unger. I think we did a video about him.
6:36Josh Clark:Yeah.
6:37Chuck Bryant:But he, you know what? I'll bet we talked about him in the Ignoble Prize episode because he won an Ignoble for this. But essentially, he conducted an experiment for 60 years because he wanted to prove his mother wrong. And he only cracked the knuckles on, I think, his left hand. Never cracked them on his right hand. That's crazy. And then after 60 years, he finally said, OK, it's time. And he x-rayed his hands.
7:03Josh Clark:Yeah. If he didn't have the compulsion to crack his knuckles, I could see how this happened. But if you are a knuckle cracker, you're kind of you feel compelled to do it. So I can't imagine what it would have taken to not crack the knuckles on one hand for that many years. It must have been really tough.
7:21Chuck Bryant:Yeah, sure.
7:23Josh Clark:That's my guess. So, yeah, he did this over his lifetime. He x-rayed himself on the reg and eventually decades later came to the conclusion that he doesn't have any arthritic difference in his hands. Case closed.
7:38Chuck Bryant:He had NAD, no arthritic difference. That's right. That's not to say, though, that even if you don't get arthritis from cracking your knuckles, it's another thing you can tell your friends at recess. Do they even have recess anymore? I guess maybe hour long screen time.
7:54Josh Clark:No, they have recess.
7:56Chuck Bryant:Okay, great. There is damage that you can do from cracking your knuckles habitually. There was a guy named Raymond Broder, and he examined 300 people who cracked their knuckles to look at what their joints looked like. And compared to the control group, no difference with arthritis again. But there was other damage, like soft tissue damage to the ligaments and the synovial fluid capsule. and that they had a decrease in grip strength. So if you crack your knuckles a lot, like don't even think about holding a glass of water with just one hand.
8:33Josh Clark:Yeah, which, you know, as you age, grip strength is important. So it's definitely not a harmless thing. There's some other possible side effects, something called ligament laxity, which is basically looseness. So over time, if you're just doing this a lot, that's what leads to the reduced grip strength and sometimes sort of overall hand function.
Read the full transcript
8:54Chuck Bryant:Yeah.
8:54Josh Clark:I think in rare cases, if you have a really weird method or forceful method or you're a little too aggressive with it, you can get some soft tissue swelling around the knuckles and the joint.
9:07Chuck Bryant:Yeah, and you can just straight-up injure yourself. You can dislocate a joint. You can injure your tendons. And even if you don't straight-up injure yourself, just habitually cracking your knuckles over time, the stretching of the ligaments can it like you said the grip strength thing um is a is a big deal just even without cracking your knuckle so um it also happens in pitchers too um major league pitchers imagine um minor league pitchers too but over the years just throwing over and over and over again they're stretching those ligaments suddenly violently basically which is kind of what you're doing when you crack your knuckles they're just doing it with different ligaments But that is why Oral Hirschheiser's right arm just dangles uselessly at his side because it's been ruined.
9:55Chuck Bryant:He ruined it pitching.
9:57Josh Clark:Yeah, I mean, I know you're kind of kidding, but sad but true. Like, especially these days, there's been more and more instances of Tommy John surgery being required because pitchers are throwing harder and harder. And if you're not, you know, able to get it near 100 miles an hour these days, you're not going to have much of a chance. So it's a real problem in baseball. That was a real bring down from my joke. Yeah. I just love that you love saying Earl Hershizer. Sure. Who else did you say? Boy, he was great. Yeah. There was a study in 1990 that confirmed the grip strength thing. I think they studied 74 people who regularly cracked their knuckles and their average grip strength was definitely lower.
10:40Josh Clark:and they had more instances of hand swelling than the 226 people who did not crack. And another interesting thing is they found that in another study that if you're a habitual knuckle cracker, you are more likely to be a manual laborer, more likely to bite your nails, as I do, smoke cigarettes, which I don't, and drink alcohol, which I do.
11:05Chuck Bryant:Yeah. So you're, you know, three for five?
11:09Josh Clark:Yeah. I don't manual labor, so we shouldn't count that one.
11:13Chuck Bryant:So there is some benefits to actually cracking your knuckles, though, too. We're not just hating on cracking your knuckles. There's something called the Golgi tendon organs, not the Golgi apparatus. It's a different episode altogether. The Golgi tendon organs sense muscle tension. And when you crack your knuckles, you're actually relieving some muscle tension. so the muscles around the joints, when you crack them, get relaxed. So you can feel like, you know, your hands feel pretty mellow after cracking your knuckles. I saw it described as yoga for your knuckles.
11:50Josh Clark:Oh, interesting.
11:51Chuck Bryant:Yeah, I thought so too.
11:53Josh Clark:Is that like getting your back cracked or something?
11:54Chuck Bryant:Basically, yeah, but for your knuckles.
11:57Josh Clark:Yeah, we found one more thing, you know, like I'm at the age where, you know, If I kneel down to get something, you're going to hear a snap, crackle, and a pop maybe coming from some part of my body.
12:10Chuck Bryant:Do you make an involuntary sound too when you're getting up? I do.
12:13Josh Clark:Oh, yeah. Like, oh, God, here we go. Yeah. Or something like that.
12:16Chuck Bryant:Like, you can't not do it.
12:18Josh Clark:Yeah, for sure. And when I walk downstairs, my right ankle, like on every step, just goes pop, pop, pop. So those things happen. I don't think anyone knows exactly where that comes from. There's speculation it could be just like, you know, if it's your knee, it may be your kneecap rubbing on the bones or something like that. Or maybe a tendon sliding over a bumpy surface or something like that. So I don't think it's anything to be alarmed about.
12:48Chuck Bryant:It is alarming, though, for sure.
12:50Josh Clark:Yeah, because it comes with age. So every new pain and sound is like, oh, that didn't happen a few years ago. Exactly.
12:56Chuck Bryant:I should go sit down for a while.
12:58Josh Clark:Right.
12:59Chuck Bryant:You got anything else for short stuff, Guy?
13:02Josh Clark:I got nothing else. I can't crack my knuckles, so... Oh, wait, there went one. Recavitated. So what does that mean? I think that means short stuff is out.
13:14Josh Clark:Stuff You Should Know is a production of iHeartRadio. For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.
13:30Thank you.
From the publisher
Does knuckle cracking give you arthritis? It doesn't appear to. But that doesn't mean it's harmless.
See omnystudio.com/listener for privacy information.
