What causes crackling knuckles?

Cracking your knuckles causes a gas bubble to form and collapse in the synovial fluid within the joints. This fluid acts as a lubricant, allowing the bones to move smoothly against one another. When you crack your knuckles, you essentially force this fluid out of the joint, allowing it to create a bubble. As the bubble passes through the joint, it bursts, releasing the pressure and creating the characteristic cracking sound.

The scientific term for cracking your knuckles is "cavitation." When the synovial fluid is rapidly displaced, it creates a vacuum that causes a separation between the fluid and the dissolved gasses within it. This separation forms the bubbles that eventually collapse and create the cracking sound.

While cracking your knuckles may feel satisfying and harmless, it's worth noting that excessive or frequent cracking can cause damage to the joint structures, such as weakening of the ligaments, joint instability, and inflammation. Therefore, it's generally advised to avoid making a habit of cracking your knuckles, especially if it starts causing pain or discomfort.