The click or pop happens on movement; it can happen unexpectedly (e.g. when you move in a certain way), or deliberately, such as cracking your knuckles, or when an osteopath, physiotherapist or chiropractor does it in a treatment. The sound itself is simply a congregation of gas molecules which are in the tissues surrounding the joint; the individual molecules are pulled into the joint space when the joint surfaces are forced/stretched apart (nature abhors a vacuum), and as they join together they form a popping sound. It is worth bearing in mind the following:
- Although it may sound dramatic and confer some expertise on the part of the person doing it, it may be of no benefit whatsoever…or, it could be exactly what is required! So, just because a joint clicks, it doesn’t mean it’s relevant to you getting better!
- Cavitating a joint can be inadvisable, for example, with acute pain into an arm or a leg, if this is caused by a disc bulge, prolapse or herniation; in my opinion this could place potentially harmful stress on an injured structure.
- Repeatedly cavitating the same area of the spine can result in hypermobility and irritability, and is difficult to justify clinically; I have had several patients who have received intensive and repeated spinal manipulation which has led to long-term irritation of that particular joint.
- There is research to show that cavitation results in a reduction in the tone of surrounding muscles by reducing alpha motor neurone activity, and increasing circulating endocannabinoids, leading to pain relief.
By the way, it’s a myth that clicking joints causes arthritis.