Why do your knuckles crack? Engineers say they finally figured it out
By Katie LanginMar. 29, 2018 , 9:00 AM
The pop of a good knuckle crack fills a room, but what actually makes the noise? Scientists have struggled to find a clear answer because it all happens so fast.
So researchers turned to mathematical formulas. They created equations describing what goes on in the fluid-filled space between the finger bones and the hand bones—the suspected source of the cracking. Then they tested a prominent idea to explain the sound: Bubbles form in the fluid-filled space when the joint expands during the act of knuckle-cracking, and some scientists think that the subsequent collapse of those bubbles is what causes the popping sound.
http://www.sciencemag.org/news/2018/03/why-do-your-knuckles-crack-engineers-say-they-finally-figured-it-out
