A 24-year-old female presented to the chiropractic clinic with low back pain and neck pain. During the chiropractic treatment, the patient enquired about the significance of the “crack” that accompanied the adjustment. The audible release is a phenomenon that is familiar to chiropractors. Although it is widely accepted that this “cracking” sound is generated by a cavitation mechanism, there are a number of opinions regarding the significance of the audible release to a chiropractic adjustment. The author wonders if there is any evidence to suggest that an audible release is a necessary component to a successful adjustment.
Three part question
For [a chiropractic adjustment] does [an audible release] improve [outcome]?
A computerised literature search was conducted on the following databases: Allied and Complementary Medicine Allied (AMED), Index to Chiropractic Literature (ICL), Manual, Alternative and Natural Therapy (MANTIS) and Medline (Pub Med). In addition the Journal of Manipulative and Physiological Therapeutics (JMPT), Spine, and the Archives of Physical Medicine and Rehabilitation where searched. The following terms where used for the search: cavitation AND (sound OR sounds) OR audible AND (release OR pop) OR joint AND (crack OR cracks OR cracking). Results where limited to English language. Results older than 20 years where not included.
82 articles where found, of which 7 were relevant.
There is some evidence to suggest that a cavitation is required during an adjustment to achieve the forces in the appropriate periarticular tissues without causing muscular damage. It is suggested that a chiropractor can accurately detect a cavitation. However, during a manipulation it is impossible to be certain which joint underwent the cavitation process based solely on the sound. Therefore, the sound of an audible release does not necessarily indicate that the appropriate reflexes were stimulated.
Possibly the greatest therapeutic benefit of the audible release may not be physiological in nature but rather psychological. The joint crack may have a powerful placebo effect on both the patient and practitioner. It is not unreasonable to assume that the patient expects to hear a cracking sound during the treatment and interprets this sound as a sign of a successful adjustment. When the expectations of the patient are not fulfilled this may have a negative affect on the clinical outcome. If an audible release is achieved, especially with reinforcement from the practitioner, then a powerful placebo effect may be expected.
Clinical bottom line
There is no direct evidence for the physiological therapeutic benefit of the audible release associated with the chiropractic adjustment. Furthermore, repeating the adjustment shortly after the joint has cavitated without an audible release, aiming to “get an audible”, may even cause damage as the joint is potentially stretched beyond its anatomical range of movement.
To conclude, an audible release may improve the outcome of a chiropractic adjustment, but therapeutic benefits of the audible release are likely to be psychological, and not physiological.
Author information: Mischa Bakker, AECC student and Joyce Miller, BSc, DC, DABCO, Senior Clinical Tutor, AECC.