In a study published Wednesday in PLOS, researchers report that they finally just threw those ivory ticklers into an MRI to see what was going on. They still have to confirm their findings, but they believe the sound that we hear when cracking knuckle joints is caused by the formation of a bubble in joint fluid.
Maybe you’ve heard that one before — it was proposed as an explanation for the popping back in 1947. But in 1971, another group of researchers claimed it was actually the collapse of that bubble that made the noise, not the formation. In the new study, University of Alberta researchers claim that modern imaging technology actually supported the older theory.
“There have always been these warring camps: The formation of the bubble makes the sound, or the collapse of the bubble makes the sound,” lead author Greg Kawchuksaid. The study came about when chiropractor Jerome Fryer approached Kawchuk about the prevalent theories and the men realized that no one had ever examined the phenomenon closely in an MRI.