What’s That Noise When You Crack Your Fingers?

No, you’re not “cracking your bones!” Can you imagine? The sound is a result of the bursting of bubbles. Xrays taken directly after “cracking” a joint show a gas bubble inside the joint. Every time you pull your finger until your knuckle cracked, for example, a bubble is formed in the synovial fluid of your joint that is associated with the popping sound. This incident happens really fast. Within 310 milliseconds. 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. Another interesting fact is that the gas is reabsorbed back into the joint within a few minutes. This is why you have to wait until you can recrack your knuckle. And lastly and for whatever it is worth noting, there is no evidence that cracking leads to degenerative changes in the joints.