CityOfAngels

I've been cracking my knuckles ever since 1992. I started off with just the big knuckles on my hands, and then went on to cracking my toe knuckles, and then on to the smaller knuckles at the tops of my fingers and my toes. Sometimes I'll even crack my back and my neck.

I've always wondered a few things about this:
a) What makes the cracking sound?
and b) Does it really cause arthritis? If so, why?

As for the sound, I've heard two theories:
a) When you add pressure to your joints, little air-pockets pop, causing the sound.
b) When you crack your knuckles, your cartilage snaps across the bones in the sudden movement.

As for the arthritis, I've also heard more than one theory:
a) You only get arthritis when you crack them in a crooked fashion. If you crack them straight without grinding the bones against each other, then there is no risk of arthritis. (I got this explanation from a few osteologists I worked with at a recent burial ground I monitored).
b) When the air pockets burst, your knuckles gradually fill up with liquid over time.
c) The cartilage gets worn down from rubbing against your bones all the time.

With all these theories, I am now more confused than I was before! Anyone know the real facts regarding this issue?

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