If you have been adjusted before, you are familiar with the usual popping or cracking sound that sometimes happens. Many people ask me what that sound is, guessing that the bones are rubbing together or its the sound of a bone popping back into place. However, what is actually occurring is something much more simple.
When a chiropractor, such as myself, sets you up for an adjustment, they are bringing your joints to tension. A joint is when two bones meet at a junction with cartilage or synovial fluid between them as a barrier or cushion. The fluid creates byproducts of natural gasses such as oxygen, CO2 and nitrogen. When a chiropractor brings the joint to tension and delivers a quick and precise thrust, they end up stretching or gapping the joint creating a bubble in in the fluid releasing the gasses causing a "POP" sound.
This sound does not, in it of itself, speak to the value of the adjustment. It can be audible despite having no sensation at all, though it could also be present when an adjustment is uncomfortable. The alignment and balance of the spine is often positively impacted regardless of the presence of this sound as well.