What do you get when you combine the "Wayne Gretzky of knuckle cracking" with a magnetic resonance imaging (MRI) machine? The answer to a very old question, it turns out.
By using MRI to video-record knuckle cracking in action, researchers have discovered that the unsettling "pop" made by cracking one's knuckles results from the rapid creation of a cavity in the fluid inside the joints.
Image: UNIVERSITY OF ALBERTA
