Fin­ger crack­ing comes from fluid be­tween joints

The sound of crack­ing fin­gers does not come from bones or ten­dons. In fact, doc­tors didn't dis­cover how the sound is made un­til 2015!

Science Illustrated - - ASK US -

1 The fin­gers are joined via a joint cap­sule filled with lu­bri­cat­ing fluid. The joint fluid is full of dis­solved air mol­e­cules such as ni­tro­gen and car­bon diox­ide. 2 When we crack our fin­gers, the joints are pulled apart, and the joint cap­sule vol­ume in­creases, caus­ing an empty space in the fluid, into which the air mol­e­cules rush, caus­ing the crack­ing sound.

BONE JOINT FLUID JOINT CAP­SULE AIR MOL­E­CULES

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