"Cracking" refers to the cracking sound that is sometimes heard during treatment by a chiropractor. A chiropractor is therefore popularly called "bone cracker", although it is not actually the bones that crack. The cause of the sound is the formation, and immediately subsequent, the explosion of small gas bubbles in the synovial fluid, when mechanical forces are exercised on the joint capsule by some manipulative techniques. In the spine, the sound originates from the facet joints. Scientific research has revealed that there is no therapeutic benefit from the cracking sound associated with chiropractic adjustment. Striking also are the results of a study into the source of the cracking sound during chiropractic spinal manipulations. In only half of the cases the sound originated from the targeted vertebra.
During an AVOM treatment there is no cracking sound.