Ask the Chiropractor: What is that cracking sound when you adjust me?

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The sound a joint makes when adjusted is often described by Chiropractors  as an“articular crack,” “articular pop,” “clunk,”“crepitus,” “joint click,” “audible cavitation” or  “snap,” Many people do not understand what is causing that sound.   I have a number of people who come into my office and tell me that they are scared of the cracking when I adjust them. Some are scared that we are breaking their bones. Well I’d like to set the information straight so that there is more understanding and less fear.

What causes the cracking sound?

Currently, the understanding of the cracking sound from a spinal manipulation is a result of what is known as cavitation.  When a joint is separated enough (within it’s natural range) there is a large reduction in pressure compared to atmospheric pressure (-3.5 atm vs 1 atm). This causes gases to escape from the synovial fluid within the joint (synovial fluid provides for a friction free surface and nourishes the joint) forming a bubble; a momentary vacuum.  The contents in this vacuum are water vapor, nitrogen, oxygen, and carbon dioxide. Eighty percent of the contents is carbon dioxide.  That bubble quickly collapses causing the cracking sound.

Edit (April 16,2015): Recent research has shown that it is in fact the opening of the joint that causes the crack and not the collapse of the bubble.

Does the cracking sound always occur?

An audible crack does not always occur even if a joint has been released.  The larger the joint is the less likely it will make a cracking sound.  It is true that the cracking sound is “dear to the ear of the bone-setter.” As a student, we knew we adjusted the joint when we heard the crack and it was frustrating  when we didn’t hear a sound. Patients feel the same way. They feel that nothing has happened if they didn’t hear the crack.  This is evidently not the case.  It is the movement of the joint that is more likely the therapeutic benefit of a manipulation and not the cracking sound.

Are “bad joints” the only ones that crack?

Any synovial joint has the potential to crack. Both healthy and unhealthy joints can be cracked.  This phenomenon does not indicate a bad joint.  Once a joint cracks there is a refractory period for approximately 20 minutes where another crack will not occur.

So remember, a chiropractic adjustment is not causing bones to break.  The cracking sound is a natural phenomenon when the joint is distracted and released. I hope this helps you better understand about the cracking sound after a chiropractic adjustment.

Dr Notley
Winnipeg’s only dual credentialed Chiropractor / Athletic Therapist

Resource
Protopapas MG, Cymet TC.Joint cracking and popping: Understanding noises that accompany articular. release. J Am Osteopath Assoc 2002 Jun;102(6):306.

Originally posted on May 17, 2022 @ 4:40 pm