That satisfying pop from knuckles or unexpected crack from knees during stretches often puzzles both medical professionals ...

Their model confirms the idea that the cracking sound is due to tiny bubbles collapsing in the fluid of the joint as the pressure changes. Surprisingly, perhaps, the phenomenon has been debated ...

On rear-drive vehicles, one sign of a worn U-join is a “clank” sound when a drive gear is engaged. On front-drive vehicles, CV joints often make a clicking noise when they’re worn.