What is cavitation in joint popping sounds?

During a chiropractic adjustment, patients often hear a popping or cracking sound from the treated joint. This sound is cavitation, which occurs when pressure changes in the joint space cause dissolved gases to form and release bubbles in the synovial fluid that lubricates the joint. The noise comes from these gas bubbles collapsing, not from bones breaking or grinding against each other.

The synovial fluid in joints contains nitrogen, oxygen, and carbon dioxide in dissolved form. When a chiropractor applies a specific force to a joint, the pressure inside the joint capsule drops suddenly. This drop in pressure allows the dissolved gases to come out of solution and form small bubbles. When these bubbles collapse, they produce the audible crack or pop that patients hear and feel. The same principle explains the sound when someone cracks their knuckles.

Cavitation is a normal and often desirable part of spinal and joint adjustments in chiropractic care. The release of pressure and gas may contribute to increased joint mobility and comfort. Some patients find the sound reassuring, while others are initially surprised by it. It is important to understand that cavitation is not harmful and does not indicate that bones are being damaged. After cavitation occurs in a joint, there is typically a refractory period before the gases redissolve and cavitation can happen again in that same joint.