--- title: Cracking Knuckles: Why Our Knuckles Crack description: Scientists have answered the puzzling question of why our knuckles make that "pop" sound when we crack them. canonical: https://time.com/3825071/heres-why-our-knuckles-crack/ author: Alexandra Sifferlin article:opinion: false article:content_tier: free article:published_time: 2015-04-16T18:11:04.000Z article:modified_time: 2026-05-11T05:04:32.436Z article:section: Health og:title: Here's Why Our Knuckles Crack og:description: Scientists have answered the puzzling question of why our knuckles make that "pop" sound when we crack them. og:url: https://time.com/3825071/heres-why-our-knuckles-crack/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltde093bcdab65f2d0/6988d9b9bc6cfc69913e2a3c/time-logo.jpg?branch=production og:image:width: 1200 og:image:height: 675 og:image:alt: TIME og:type: article twitter:card: summary_large_image twitter:title: Here's Why Our Knuckles Crack twitter:description: Scientists have answered the puzzling question of why our knuckles make that "pop" sound when we crack them. twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/bltde093bcdab65f2d0/6988d9b9bc6cfc69913e2a3c/time-logo.jpg?branch=production --- # Here's Why Our Knuckles Crack by [Alexandra Sifferlin](https://time.com/author/alexandra-sifferlin/) ## Alexandra Sifferlin Apr 16, 2015 6:11 PM UTC by [Alexandra Sifferlin](https://time.com/author/alexandra-sifferlin/) ## Alexandra Sifferlin Apr 16, 2015 6:11 PM UTC Scientists have answered the puzzling question of why our knuckles make that “pop” sound when we crack them. A team of University of Alberta researchers had a volunteer crack his knuckles inside an MRI scanner so the researchers could figure out what was going on. They [published their findings](http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0119470) on Wednesday in the journal _PLOS ONE_. The researchers have concluded that the crack comes from a gas-filled cavity or “[bubble](http://www.npr.org/blogs/health/2015/04/15/399636388/why-knuckles-crack)” that forms in the fluid between the joint. “It’s a little bit like forming a vacuum,” said lead study author Greg Kawchuk, a professor in the Faculty of Rehabilitation Medicine [in a statement](http://rehabilitation.ualberta.ca/news/2015/april/pull-my-finger-say-scientists-who-solve-knuckle-cracking-riddle). “As the joint surfaces suddenly separate, there is no more fluid available to fill the increasing joint volume, so a cavity is created and that event is what’s associated with the sound.” **MORE:** [You Asked: Is Cracking Your Knuckles Bad?](http://time.com/3529225/cracking-knuckles-arthritis/) The study supports an original theory from the 1940s, the researchers say. But in the 1970s, other researchers believed that the sound came from a bubble collapsing in the joint instead. But is cracking your knuckles bad for you? That little bubble appears to be benign; [there’s no evidence](http://time.com/3529225/cracking-knuckles-arthritis/) to suggest that people who crack their knuckles are more likely to suffer from arthritis than those who don’t. ### You Asked: Your Top 10 Health Questions Answered  You Asked: Are Cleanses Healthy? Potions that claim to clear your body of toxins might sound alluring, but do they deliver? Illustration by Peter Oumanski for TIME  You Asked: Is Eating Dessert Really That Bad For Me? Bad news for sweet-eaters—except if you end your meals with this kind of treat. Illustration by Peter Oumanski for TIME  You Asked: What’s the Best Way to Whiten My Teeth? Yes, teeth whitening actually works—but here's why you have to dish out major bucks to see results. Illustration by Peter Oumanski for TIME  You Asked: Is Meditation Really Worth It? From easing stress to lowering heart disease risk, focusing your mind can do some amazing things for your body. 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