Knuckle-Cracking Sound Explained

Using MRI, researchers recorded in real-time what happens inside a joint when it joint separation was associated with rapid creation of a gas-filled cavity within the synovial fluid, a slippery substance that lubricates the joints. Rapid cavity inception at the time of joint separation may cause the popping sound heard. Credit: Real-Time Visualization of Joint Cavitation Gregory N. Kawchuk, Jerome Fryer, Jacob L. Jaremko, Hongbo Zeng, Lindsay Rowe, Richard Thompson PLoS ONE April 15, 2015 do