Do you enjoy cracking your knuckles? Some people are repulsed by it and some are inexplicably drawn to it, but the controversy doesn’t extend just to cracking preferences. Scientists have been fascinated with the cause of the cracking sound for decades, suggesting different theories about the nature and safety of knuckle-cracking.
One of the oldest theories about fluid in the joint is gaining traction again as researchers have discovered new information about why our knuckles crack. The knuckle is composed of a pocket of fluid between two finger bones, with carbon dioxide and other gases dissolved in the fluid. The liquid cushions the bones to keep them from grinding against each other, but when the bones are pulled apart the pressure drops and a gas bubble forms inside the fluid. When the bubble collapses part or all of the way, it creates that familiar noise.
The good news is, the sound is not your bones rubbing together, as some people think. But the case of whether this practice is detrimental in the long term has not yet been cracked.