The Science of Knuckle Cracking: What Really Causes the Sound?

Cracking knuckles bursts a synovial fluid bubble in the joint. Synovial fluid lubricates and cushions joints. Pulling/twisting creates negative pressure, drawing fluid into the cavity to form a bubble; its collapse releases a sound wave.

Knuckle cracking doesn't cause arthritis but can become habitual. Excessive cracking may loosen finger ligaments over time.