Real time visualization of joint cavitation

Despite decades of research, the underlying mechanism associated with joint "cracking" has yet to be scientifically validated. Until recently little was known regarding the process by which noises were emitted from the joint when distraction forces were applied. The current study utilized real-time MRI for the first time to visualize the MCP joint space while a long-axis traction force was applied.

An adult male with the ability to crack his MCP joints participated in the study. During distraction, cine MRI was obtained of the midline point of the joint at a rate of 3.2 frames a second.

The author’s results support a previously defined theory known as tribonucleation whereby it was believed that cracking was a result of cavity inception rather than pre-existing bubble collapse. Dark signal intensities in the joint immediately following cracking verifies the production of an air region in the joint space that persists past the point of sound production. By characterizing the underlying etiology of joint cracking the authors hope to better understand its therapeutic advantages and disadvantages.