Blog: Snap, Crack & Pop!

07 July 2017

Love it or loathe it, we all know that one person who is constantly cracking their knuckles (or if not, then maybe you’re the culprit).

According to Medical News Today, between 25 and 54% of us are knuckle crackers whether it’s pulling each finger one at a time, making a tight fist or bending the fingers backwards away from the hand (or perhaps you’re even more creative). For some the habit can accompany concentration while for others it can be the result of nerves, as the cracking sound can bring a feeling of relief (there are also those that enjoy to sit and crack their knuckles to make others wince).

But what happens in your hand to create a sound which is simultaneously incredibly satisfying and uncomfortable?

Regardless of their (or your!) go-to knuckle cracking method, the same thing happens. The gap in between the joints increases which causes the gases (oxygen, nitrogen and carbon dioxide to be precise) dissolved in synovial fluid, the fluid which acts as a lubricant for your joints, to be rapidly released and form bubbles. These bubbles are initially microscopic but then merge and grow in size. The bubbles are only short lived as they’re popped by the additional fluid which rushes in to fill the enlarged space.

You may or may not have noticed that you have to wait a certain amount of time before you’re able to crack the same joint again. This is because the gases have to return to the synovial fluid, which should take roughly 15 minutes (that’s plenty of time to make yourself a nice sandwich).

When you stand up after a long period of time of being sat down, you may find that your knees seem to protest with a similar cracking sound. What’s happening here is while you were sat down your joint moved your tendon’s position slightly out of place, so when you stood up your tendon snapped back into its original position and therefore making the sound (remember, bend and snap works every time). You’ll find that this is very common in your knees and ankles.

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A pair of hands