Serial knuckle cracking

Notice the white spot in the joint as the bones separate.
Credit: Gregory Kawchuk, University of Alberta/Plos Media/Wired

Most surprising part of this for me — the revelation is that the cracking sound is caused by bubble formation as the joint comes apart — this was always my understanding.

http://www.gizmodo.com.au/2015/04/mri-video-reveals-what-it-actually-looks-like-when-you-crack-your-joints/

http://www.wired.com/2015/04/watch-gross-mri-knuckle-cracking/ / knuckle cracking crack joints scientists never really understood physics chilling noise 1970s experts collapse gas nitrogen air bubbles synovial fluid lubricates joints new evidence sound formation gas-filled cavity joints stretch apart study researchers University of Alberta crack his knuckles multiple scientists fingers magnetic resonance imager watching cracking events researchers video bones in the joint separate negative pressure gas nitrogen synovial fluid sudden formation of bubbles scientific term tribonucleation crack pop flash space joint surfaces separate MRI signal cavitation tribonucleation joint surfaces come together bubble rapidly collapses popping phenomenon medical insight study Jacob Jaremko radiologist University of Alberta bubble collapse shock damage surrounding structures cavitation latest study provides some new information on the physics behind joint cavitation researchers research effects bubble collapse places of the human body flow dynamics heart circulation bloodstream fluid under pressure tribonucleation effects large consequences crack /