MRI cracks the case of knuckle-popping puzzle

 - Left hand

For some, cracking their knuckles is a nervous habit or part of a stretch routine during the workday. Others are sure it must cause damage or lead to arthritis. But until recently, nobody was certain about how the noise was even created. A team of researchers turned to MRI for the answer.

Led by researchers from the University of Alberta, the team looked at MRI video to determine a vacuum cavity rapidly forming inside the joint is the source of the distinctive sound. You can read the study they published on the subject in PLOS ONE. A sample MRI video and a press release from the University of Alberta are available below: