What really happens when you crack your knuckles?

When you crack your knuckles, you are actually causing a bubble of synovial fluid to burst inside the joint. Synovial fluid is a clear, viscous liquid that acts as a lubricant and shock absorber in joints. When you pull or twist your finger, you create a negative pressure in the joint, which causes the synovial fluid to be sucked into the joint cavity and form a bubble. When the bubble bursts, it releases energy in the form of a sound wave, which is what you hear when you crack your knuckles.

Cracking your knuckles is not harmful, and it does not cause arthritis. However, it can become a habit, and if you do it too often, it can cause the ligaments in your fingers to become loose and weak.