What is the “cracking” or “snapping” noise experienced with some adjustments?

During some techniques of applying a chiropractic adjustment a common experience is a cracking or snapping noise. This experience is new to most people since they are not familiar with hearing their own body produce noise. In chiropractic we refer to this noise as a “Release”, and a release is simply the production of gas being released from the joint cavity. The easiest way to understand this is using a suction cup. A suction cup is stationary similar to a joint that has a lack of mobility, once that suction cup is pulled it the back pressure that was holding it in place releases and creates a popping or crack noise; this is exactly the same thing that happens when one of your joints loses mobility and then your chiropractor applies a pressure to move the joint. Please remember that a release or crack is not required for an adjustment to take place, however for some individuals it adds a psychological benefit.