[rookie]

I read somewhere that the sound you hear when u crack your knuckles is actually the sound of nitrogen gas bubbles bursting... is this true?!  

[P]

I recently found out that a whip crack is due to a mini sonic boom as the whiplash causes the end of the whip to break the sound barrier. They slowed down a video and worked out the speed of the whip to be about 800 (ish) miles an hour.

wrt your question I'm afraid I don't know  -  I stand to be corrected but I think it is an unlikely explanation.

[billnotgatez]

It is actually your cartilage screaming in pain and pleading for mercy.

[savoy7]

The "sudden" movement of fluid in the joint (synovial) from one side to another causes that noise.  The sudden is relative to the normal movement of the fluid.

I have read no article that statistically links cracking knuckles to joint issues.

I have concluded that it does disgust my wife.

[Organishe]

I've actually heard that the original explanation given is the correct one: in the process of popping your knuckles, the pressure within the joint capsule is lowered sufficiently to allow dissolved nitrogen/other gases in the synovial fluid to gassify, forming tiny bubbles that burst, creating the pop. It then takes a few minutes to redissolve, hence giving an explanation as to why it takes a few minutes before you can pop your knucle again. 


http://en.wikipedia.org/wiki/Cracking_knuckles


So, I wouldn't say it is definite, but the majority of sources I've found do seem to agree on this explanation.


Ta