Video: Here's what it looks like inside your finger when you crack your knuckles
This video shows you exactly what goes on inside a finger that is having its knuckles cracked, plus how the popping sound happens.
While some people can't stand it, for others it is a regular habit. But 'knuckle cracking' has been brought to life like never before by this clever video.
Using an MRI scanner, researchers were able to show the world exactly what goes on inside a finger undergoing the process.
It shows the two joints meeting, and the release of gas from the synovial fluid coating the cartilage. This gas creates a cavity and it is the rapid creation of that gap that makes the infamous 'cracking' or 'popping' sound that can set some people's teeth on edge.