How do Chiropractors crack your back?

How do Chiropractors crack your back?

The cracking sound during an adjustment is merely a minute amount of gas between the joints being released.

The Chiropractor applies a quick adjustment to a joint (with his hands or with an instrument) and the joint moves back into proper alignment.  Usually one will here a "crack" sound when the gas is released from between the adjusted joints.

Here's a video showing some of the tools used and how an adjustment is delivered to the joints of the body. http://www.youtube.com/watch?v=YMpNJidksAw