New MRI Study Disproves Popular Knuckle “Cracking” Theory

Have you ever wondered what’s happening when someone cracks their knuckles?  So many of us do it.  I know my grandmother would always fuss me for doing it, telling me it was going to cause arthritis.  Later, it was explained that it was the rapid disipation of a single bubble in the joint to many smaller bubbles.  But, now, a new study with real-time MRI evidence shows exactly what is going on when we crack our knuckles.

Researchers used a cable to pull a man’s fingers while watching them on an MRI scanner.  The video shows the knuckle separating and a bubble of gas forming inside the synovial fluid (the fluid in between joints that acts as a “lubricant”)  The cracks lasted for about 1/3 of a second.  But, contrary to what has been previously explained, the bubble did not burst.  It is slowly reabsorbed over a 20 minute period making the re-cracking of knuckles difficult/impossible.

“It’s a little bit like forming a vacuum,” said study author Greg Kawchuk in a media release. “As the joint surfaces suddenly separate, there is no more fluid available to fill the increasing joint volume, so a cavity is created and that event is what’s associated with the sound.”

And, just to let you know, it doesn’t cause arthritis.  The complete study can be read HERE.  So, now there is one less mystery in the universe.  View the video below to see the MRI of the study in action.