Why Knuckles Make a Popping Sound When Stretched

In a snappy Ted-Ed lesson written by Eleanor Nelsen and animated by Belfer Creative, narrator Addison Anderson explains exactly why knuckles and other joints release such as satisfying (or disgusting to some) popping sound when stretched. Cracking knuckles is simply the release of gas bubbles from joint cushioning synovial fluid, much in the same way gas bubbles are released when the cap is taken off a bottle of carbonated liquid.

Some people love the feeling of cracking their knuckles, while others cringe at the sound. But what causes that trademark pop? And is it dangerous?

via Geeks Are Sexy