A whole lot of people crack their knuckles. And they don't just do it occasionally - many people do it habitually, barely even noticing that they're doing it. But is it bad for you?
As the Vox video above explains, it all comes down to the fluid that surrounds our joints, called synovial fluid. When you stretch your joints, you release gas in the fluid, which forms into little bubbles. When your joints settle back into place, those bubbles burst and make a cracking sound. Want to crack the same knuckle twice? You're gonna have to wait another 20 minutes for the gas to accumulate again.
Sounds pretty harmless, right? But what does science say about this curious habit? Californian medical doctor, Donald Unger, decided to investigate, and dedicated 60 years of his life to the pursuit of the answer. And by that I mean he spent 60 years cracking the knuckles on one hand, and 60 years not cracking the knuckles on the other, so he could compare the effects.
Not only did the effort earn him an Ig Nobel in 2009, but it dispelled a long-standing myth that cracking your knuckles increases your risk of developing arthritis. Watch the video above to find out the results, and discover the real dangers associated with knuckle-cracking. (Hint: it has to do with driving everyone around you insane.)