March 2022 blog.
Text from Dr Mark Jessop, chiropractor and BC Chiropractic Association.
As chiropractors one of the many techniques we use and probably the technique chiropractors are most famous for is manipulation or “chiropractic adjustment”. Manipulation involves a quick, specific movement of a joint and is often accompanied by a popping or clicking sound. But what causes that popping sound during manipulation? The proper technical name for this sound is joint cavitation.
Is your back out?
We are often told by patients that their back is “out” and they need me to “put it back”. Is the pop the back going back in? Modern science has now shown that this is not the case and a patient’s back is not “out.” If it was manipulation certainly would not be appropriate. So when people have back pain or neck pain and their back is manipulated what is the sound? Is it the bones cracking? Again this is not the case, although it might sound like it is.
So what causes that popping sound?
In a study published in Plos One, an international team of researchers led by the University of Alberta used MRI video to determine what happens inside finger joints to cause the distinctive popping sounds heard when cracking knuckles. For the first time, they observed that the cause is a cavity forming rapidly inside the joint.
In every instance, the cracking and joint separation was associated with the rapid creation of a gas-filled cavity within the synovial fluid, a super-slippery substance that lubricates the joints.
|Static MRI of the hand in the resting phase before cracking (left). The same hand following cracking with the addition of a post-cracking distraction force (right). Note the dark, interarticular void (yellow arrow). Source: Dr. Greg Kawchuk.|
“It’s a little bit like forming a vacuum,” said professor and lead author Greg Kawchuk, Faculty of Rehabilitation Medicine. “As the joint surfaces suddenly separate, there is no more fluid available to fill the increasing joint volume, so a cavity is created and that event is what’s associated with the sound.”
So what happens if there is no sound during the adjustment?
Manipulation has been shown to be effective in the treatment of many musculoskeletal issues such as back pain and neck pain. But how does it work and is the pop important? The mechanism of how manipulation works is complex and not a case of pushing the bones back into place because they are out of line. Although it can sometimes be nice for the patient to hear the pop as it confirms something has been done, it is not essential for therapeutic benefit.
To read Dr Greg Kawchuck research paper: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0119470