One of my patients recently asked me why, when performing a manipulation, do their joints make that ‘Cracking Sound’ and does it really do anything? She also asked me if there was any purpose in trying to put joints back in place?
How I love these questions (Big Smile). I told her it was simple. It is very similar to Thanksgiving when you pull apart a wishbone. Just Kidding (I do have a warped sense of humor). I explained that the sound was primarily coming from the release of gas (80% carbon dioxide) in the joint. Furthermore, that about 15% of our joint volume (where the synovial fluid is located) is made up of gas.
I then explained to her that in addition to the immediate benefit received from increased range-of-motion in the joint, the manipulation also generates some very beneficial neurological effects. Essentially, cavitation (cracking – love that phrase) of the joint is a very effective way of initiating a neurological response called a Reflex Action (from periarticular receptors).
Most back injuries involve both the joints and the soft tissue structures around the joint (paraspinal muscles, ligaments, tendons, joint capsules etc). Essentially when you are injured the neurological receptors around your joints (mechanoreceptors and nocieptors) cause your joints and muscles to become very hypertonic (increased capsule tension, increased nerve ending sensitivity, and tight restricted muscles, all of which causes pain). Due to the abnormal motion patterns that then develop spinal joint compensations (restrictions) also commonly occur in injuries to the; shoulders, arms, hips, knees, ankles and feet.
Vertebra don’t go out of place
I do not know where this idea comes from but vertebral joints do NOT go ‘out of place’ unless they are subluxated. A subluxated vertebra refers to vertebra being partially dislocated, and this does NOT occur without significant trauma. Saying that “the joint is out of place gives” the impression that the joint somehow jumped out of position. This just does not happen as each facet joint is held firmly in place by a strong fibrous capsule.
When we look at the anatomy of the spine, we can see that each vertebra has two posterior (facet joints) and an intervertebral disc between adjacent vertebra. The function of each pair of facet joints is to guide and limit movement of each spinal segment. Depending on the section of the spine, (cervical, thoracic, or lumbar) the facet joints are orientated at a different angles. This allows for motion while limiting certain movements in order to provide stability and protection for the spine. Therefore, basic anatomy of the spine stops the joints from ‘going out of place’.
However, what commonly occurs in spinal joints is a lack of mobility (hypomobility). This is often caused by arthritis, thickening or scarring of the joint capsule, or soft-tissue restrictions.
Back to the “Cracking” – Pun Intended
When a spinal joint is manipulated (cavitated/cracked), it creates a reflex action in all the surrounding neurological joint receptors (mechanoreceptors and nocieptors). This in turn cause the surrounding joint capsule to release, hypertonic muscle to relax, and the nerve endings to become less sensitive, which together results in decreased levels of pain.
Think of the sound of joint cavitation as a very positive occurrence. Joint cavitation is an indication that the ‘Neurological Reflex Response’ has been activated. Joint cavitation is most often followed by an increase in joint range of motion, decreased soft tissue hyper-tonicity, and a decrease in pain.
A considerable amount of my practice involves soft-tissue work where we combine Active Release, Graston, Fascial Manipulation, and Acupuncture with functional exercise programs. But, as a practitioner if I did not address spinal joint restrictions, my success rate would be greatly reduced. None of the soft tissue techniques I just mentioned can activate the periarticular “Reflex Reponses” the way that joint cavitation can. Nothing frees up a restricted joint and restores joint function like joint manipulation. Joint manipulation in the hands of a trained practitioner is a highly effective safe form of therapy.
Bottom line, your spinal joints are a key component of your kinetic chain. Joints restrictions are a significant part of most injuries and cannot be overlooked. We are always talking about the fascial connections between different muscle groups and how the whole body acts as a single functional unit. Spinal joints are a key component in that kinetic web.
My advice is that if you are injured, to address all the structure of your kinetic chain, both soft tissue and osseous. Don’t leave a key aspect of your injury unattended. If you are not injured an occasional adjustment is a great form of injury prevention. I recommend most patients have a adjustment at least once every month or two.
1. The audible release associated with joint manipulation. J Manipulative Physiol Ther. 1995 Mar-Apr;18(3):155-64. Brodeur R. http://www.ncbi.nlm.nih.gov/pubmed/7790795
2. Spinal manipulative therapy and somatosensory activation. J Electromyogr Kinesiol. 2012 Oct;22(5):785-94. doi: 10.1016/j.jelekin.2012.01.015. Epub 2012 Feb 19. Pickar JG1, Bolton PS. http://www.ncbi.nlm.nih.gov/pubmed/22349622