Why do our knuckles crack?
It’s fairly well known what knuckle cracking is, its effects on humans and why it makes sound. According to howstuffworks.com, there is a certain fluid in our body called synovial fluid. This liquid surrounds every joint in our body, helping to keep the cartilage moving smoothly like oil on a gear. When you do a standard knuckle cracking action (stretching your fingers, bending your joints and so on,) the joints stretch apart, causing the pressure of the fluid to drop. This forms gas bubbles through cavitation, and if the joint is stretched far enough, the bubble will burst, causing that well known sound. It will then take about half an hour for the gas to dissolve back into the synovial fluid, and the knuckle cracking process can begin all over again. And while constant knuckle cracking doesn’t lead to arthritis as once thought, it can lead to swelling and other problems.