Medicine
What causes knuckle cracking—and could it affect joint health?
Quick fact
Knuckle cracking is caused by cavitation—the rapid formation and collapse of gas bubbles in synovial fluid when the joint is pulled apart, creating that distinct popping sound.
Why this is interesting
The sound of a cracking knuckle isn't bones grinding—it's a bubble of gas imploding in your joint fluid, and it takes about 20 minutes for that bubble to reform, which is why you can't crack the same knuckle twice in a row.