Joint Cracking – What’s Going On?

By: Eric Walper, Physiotherapist

I have always been fascinated by the phenomenon associated with joint cracking. You all know what I’m talking about that popping sound followed by the feeling of satisfaction that we all got when we cracked our knuckles and backs growing up. How many times have our parents and grandparents told us to cut it out because the cracking was somehow bad for our bodies or was going to cause arthritis?

With this in mind, I want to share with you two of my favorite research articles on the subject that will help shed light on this phenomenon.

What’s really going on with joint cracking

Joints are areas where two bones unite and are usually lubricated by fluid. In 2015, researchers at the University of Alberta [1] imaged joint popping for the first time in real time using MRI. This was the first time in history that a joint was visualized while the actual pop occurred. Research found that as a joint was pulled apart an open space began to develop within it and up until the point at which the pop/crack occurred. The amount of force or effort was proportionate to the amount the joint stuck together.

If you need help visualizing this process, think about cracking a joint like a Chinese finger trap. As you start to pull your two fingers apart in the trap, it becomes harder and harder to pull because the force of the two fingers are opposing one another. Eventually, you will pull hard enough to pop one of the fingers out, similarly to when you crack a joint. Essentially, what was discovered was that the cracking noise is due to the creation of an air bubble within it.

Is cracking my knuckles actually bad for me?

Now that’s all fine and dandy, but is cracking my knuckles actually bad for me? In 2004 [2], an interesting study was published in which a researcher cracked his knuckles of one hand daily for 60 years while leaving the knuckles on the opposing hand completely untouched. What the researcher discovered was that after 60 years of consistently cracking his knuckles, there was zero difference functionally between both his hands. When both hands were imaged to compare to one another, there was also no significant difference, putting the age-old myth that knuckle cracking causes arthritis to rest.

What does this mean?

These two studies are important to me for a couple of reasons:

1.  It helped me understand where the noise within a cracking joint actually comes from.
2.  Research demonstrated the sound had less to do with re-aligning a joint and more to do with the changes in pressure within the joint.
3.  With respect to health and safety, we can fairly confidently say that extended joint manipulation over a period of time will not have adverse effects on its health. This is an important consideration both for us as practitioners and you as patients going about your day-to-day lives.

Feel free to reach out if you have any additional questions on the subject or you can book an appointment online by clicking here.

References:

[1] Kawchuk et al., PLoS One 10 (2015) e0119470.

[2] Unger DL. Does knuckle cracking lead to arthritis of the fingers? Arthritis Rheum. 1998;41:949–950.