All information is from the, 'Why do joints click?' and 'Here's what happens to your knuckles when you crack them' video.
The most common explanation on why your joints sound like bubbles popping is well, there are bubbles in there. When you stretch out that joint, you are releasing gas, and that gas forms a bubble, it collapses and pops. The joints in your fingers are the easiest to crack, but many people also crack their hips, wrists, shoulders, necks, shoulders and so on.
Knuckle-crackers know that to get that satisfying pop, you stretch the joint farther than it normally goes by bending your fingers backwards, for example, when that happens, the bones move away from each other. The space between the bones gets bigger, but the amount of synovial fluid stays constant. That creates a low-pressure zone, that pulls dissolves gases out of the synovial fluid, that pulls dissolved gases out of the synovial fluid, just like the carbon dioxide that fizzes out of soda when you twist open the cap. Inside the joint, the escaping gases from a bubble with a pop.
The reason knuckle cracking is like that because it contains lots of dissolved gas molecules, like other fluids in your body. But the bubble doesn’t last long. The surrounding fluid presses on it until it finally collapses. The bubbles gases scatter throughout the synovial cavity and slowly dissolve back into the fluid. In order to crack the same muscle again, you have to wait for around 20 minutes for the gas to return back to that fluid.
Some scientists think there may by two pops. One when the bubble forms, and other when it bursts. Dr Donald Unger was a self-described researcher who chose to pop the joints in one of his hands for 50 years but not the other one and he wanted to find out if popping your knuckles would actually five your arthritis. After 50 years of doing it, he found that he didn’t have any more arthritis in one hand than the other.
There is still a chance it’s not good for you. One 1990 study did find that cracking your knuckles over a long period of time led to hand swelling and decreased scrip strength, but there hasn’t been any follow-up research on that. While knuckle cracking might not be bad for you, there’s still no guarantee that your popping habit won’t annoy the people around you.
