“Stop crackin’ your knuckles, you’re gonna get arthritis”
This old adage has been floating around for decades. It kinda makes sense- your bones are being manipulated until you hear a “pop”. But what actually happens when you crack your knuckles? Let’s find out.
The picture above is a diagram of a joint, more specifically a synovial joint. The knuckle cracking phenomena actually takes place in the synovial fluid. The role of synovial fluid is to keep the joint lubricated and prevent friction. It is essentially like the WD-40 of the skeletal system.
One of the key components of synovial fluid are the gases that are dissolved in it, notably carbon dioxide and nitrogen. When a joint is “cracked”, the space in between the two bones increases. This separation essentially creates a vacuum inside of the joint that forces the gases to separate from the fluid and occupy the space in between the bones. It looks like this:
All in all, it has in fact that cracking any joint does not cause arthritis. However, the verdict is still out as to whether or not it has long term effects on joint health.