What Is Happening When I Crack My Knuckles And What Is The Cause Of The Cracking Sound?
If
you crack your knuckles you are among millions of people around the world who
enjoy doing so. Many do this to relieve pressure, especially in the back. But when
we crack our knuckles, what is going on
inside and what causes that cracking sound
we hear?
Most believe the cracking sound is cause by
two joints or bones clicking against each
other.
Scientists have debated since the mid
1040's, and since no one could make up their
minds, a group of scientists from the University of Alberta decided to
perform a detailed study that would finally settle the
argument and mystery. Their study/ investigation,
was nicknamed the “pull my finger
study.” In real-time using cine magnetic resonance imaging
(MRI) they captured joint cracking. In order
to accomplish this, one of the study authors was placed
inside an MRI machine with cables
attached to his fingers which were slowly pulled until they
cracked.
They found that the sound was associated with the rapid formation of a gas-filled cavity within the lubricating fluid surrounding the joint, which remained visible after the noise was produced.
“It’s a little bit like forming a vacuum,” explains lead author Greg Kawchuk. “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.”
Watch the video below to observe knuckle
cracking in real time:
