Manipulation is a passive technique where the therapist applies a specifically directed manual impulse, or thrust, to a joint, at or near the end of the passive (or physiological) range of motion. This is often accompanied by an audible ‘crack’. The common feature of spinal manipulation techniques is the fact that they achieve a pop or cracking sound within synovial joints. The cause of this audible release is open to some speculation but it is widely accepted to represent cavitation of a spinal facet joint. When there is a lower pressure than normal in the facet joint, gas bubbles are being formed in the joint. At the moment that the pressure rises, the bubble implodes, this is called cavitation.
Effects of Manipulations
Spinal manipulations can relieve back pain by taking pressure off sensitive nerves or tissue, increase range of motion, restoring blood flow, reducing muscle tension, and, like more active exercise, promote the release of endorphins within the body to act as natural painkillers.