The most common joints in the human body are the athletic joints, such as the knuckles and shoulder joints, where a capsule holds the two bones together. Inside the joint capsule is a lubricant called synovial fluid, a substance that contains dissolvable gases. By stretching the joint, you are actually compressing the capsule and its fluid, forcing the nitrogen-rich gases to escape from the lubricating solution. When the joint capsule releases the “gas”, you hear a “popping sound”. As the gas is released, the joint becomes more flexible. But you may notice that you can’t get the same joint to pop again right away. Why is this? That’s because the released gas has to be reabsorbed by the fluid before it can make the sound again, a process that takes about 15 to 30 minutes. If you’re used to releasing stress by snapping your knuckles, you might want to try taking 30 seconds to focus on breathing deeply. While knuckle snapping doesn’t cause arthritis, it can weaken the grip of the joint. And of course it has to do with muscle imbalances that require a bit of corrective training.