Patients often ask what is responsible for the “cracking” noise sometimes heard during an adjustment and, until relatively recently, chiropractors were asking the same question! The previous theory was that the collapse of an air bubble made within the joint during a manipulation was the cause of this noise, similar to gas bubbles being released from a can of Coke when opened. However, a real time MRI study published in 2015 showed the process of a joint cavitation (aka knuckle cracking). By looking at the video in slow motion, the researchers noticed that the air bubble still remained after the “cracking” noise was heard. Therefore, it couldn’t be attributed to the previously theorized collapse. Instead, it was found that the noise came from the formation of the air bubble itself.
See the brief video here: https://www.youtube.com/watch?v=_ZNENkkf5Uw
What Does This Mean for Patients?
It’s worth knowing the science behind what is causing this noise for anyone who might be hesitant about incorporating adjustments as part of their treatment plan. I strongly recommend watching the video to understand that the “cracking” noise really isn’t cracking at all.
And remember: manipulation should not be the only tool in a chiropractor’s toolbox. I urge patient’s to talk to their chiropractor about any questions, concerns, or preferences they may have when it comes to treatment.
Kawchuk GN, Fryer J, Jaremko JL, Zeng H, Rowe L, Thompson R (2015) Real-Time Visualization of Joint Cavitation. PLoS ONE 10(4): e0119470. https://doi.org/10.1371/journal.pone.0119470