No – it’s not your bones cracking. There has been great debate over the past few years as to what causes the popping sound when you receive an adjustment. Some research has shown that it is the formation of gas bubbles that causes the audible ‘pop’ due to the pressure change in the joint when it is stretched. Other research suggests that it is the actually the collapse of the bubbles that creates the signature noise of an adjustment. So which is it?
The most recent evidence suggests that it is the collapse of the air pockets/bubbles that make the popping sound. There is no doubt that stretching or pushing a joint just past its normal physiological range (which is what occurs during an adjustment) creates a lowered pressure in the joint and air bubbles are created, but it seems that it’s the subsequent collapse of these bubbles that gives us the sound.
These bubbles were found to have the same ‘acoustic signature’ as the audible ‘pop’ by the mathematicians from Stanford who did this investigation. Interestingly, in some subjects the bubbles remained around the joint after the adjustment was completed, so how could the collapse of the bubbles be responsible for the sound? The researchers explained that even a partial collapse of the bubble can provide the popping noise – it doesn’t have to be a complete collapse.
Would we be surprised if a new article came out next month to contradict this research? Absolutely not. But for now – this is what we’re going to go with.
What we can be sure of is that it’s the gas in the joint that causes the noise. Is it the formation or the collapse? The best evidence right now suggests it’s the collapse. Similar to opening a pop can and releasing the pressure, the collapse of these bubbles and release of the gas around the joint can release pressure as well!
Watch a video that shows a real-time MRI of a knuckle being adjusted to see the formation of the gas bubbles and eventual collapse. The little black space that occurs during the adjustment is the gas formation!
Another fun fact: despite what your mother probably told you as a kid – you will not get arthritis from cracking your own joints. A doctor cracked the knuckles on one hand for SIX DECADES, and left his other hand alone – he never cracked it once. No sign of arthritis in either hand! Imagine being dedicated enough to continue your experiment for 60 years?