What is that “crunching” noise that I hear when the Doctor adjusts my spine?
The audible noise during an adjustment is called “cavitation”. This sound is not caused by bones “cracking”. Inside the joints, there is a lubricating fluid that is secreted by the lining of the joint capsule. One of the waste byproducts of cellular metabolism is nitrogen gas. It forms tiny bubbles throughout the fluid in the joint, similar to a glass filled with a clear carbonated drink like “Sprite” or “7-Up”. When you bump the glass, the bubbles dissipate and pop, creating the fizzing noise that you can hear. When an adjustment is made, the nitrogen gas bubbles inside the joint react much the same way, causing the “popping” noise. Depending on the amount of gas bubbles in a joint, the noise is less or greater at different times.
