In April, a group of scientists made a cracker of a claim: They finally figured out why knuckles crack. But now other researchers are on the case. A study presented Tuesday at the annual meeting of the Radiological Society of North America takes a deep dive into the science of the knuckle crack.
The big knuckle debate centers on one big question: What makes the cracking sound? Back in 1947, it was suggested that the sound occurred when a bubble formed in the fluid between joints. But in 1971, another group claimed it was actually the collapse of that bubble that made the noise, not the formation. The April study seemed to confirm the latter by tracking the cracking inside an MRI.
In the new study, knuckles were cracked under the watchful gaze of an ultrasound machine. The study provides solid evidence that the changes in pressure associated with joint fluid bubbles are the cause of knuckle cracks.
The study also found that after a joint cracks, the range of motion for that joint increases significantly and there were no signs of ill effects.
