What is the popping when you get a chiropractic adjustment?

Answer 1

After most chiropractic adjustments you will hear a pop or crack sound. Chiropractors often refer to this sound as an "audible" or a "cavitation."

The sound is actually the formation of gaseous bubbles in the joint space. This occurs because the joint-space is an enclosed, fluid-filled space and when an adjustment is performed often that space is opened, such that the volume is increased. Laws of physics teach us that pressure and volume are inversely related (see ideal gas law PV=nRT), therefore an increase in volume will result in a decrease in pressure. This is called negative pressure and results in the portion of the fluid turning into gas bubbles. When this occurs an audible "POP" is heard.

It is a common misnomer that either a bone is "popping back into place" or that bones are hitting bones, this is not the case. The sound after a chiropractic adjustment is NOT bones hitting bones, it is just a reaction within the fluid of the joint space responding to decreased intraarticular pressure.

Answer 2

Before you get a chiropractic adjustment, the chiropractor palpates your spine to detect any subluxation present (any loss of mobility in the joint) and that would be the area where you are going to get the adjustment.

Once he/she contacted your back, with a specific technique, he/she will give you a quick, low force impulse which will result in the popping sound. The sound that you hear is the joint opening up. Because it wasn't moving as it was supposed to, it got stuck by a substance (sticky).

On the contrary of what you might have heard about cracking bones, it is the joint that moves. One easy example of this would be your middle finger from your hand. You can grab that finger and pull it slowly until you reach a taut point. Then with a little impulse (pull), you can actually hear the "popping" sound of your metacarpophalangeal joint opening (gapping).