Ultrasound Knuckle-Cracking Fireworks

Wissenschaftler haben Gelenkeknacken mit Ultraschall-Video aufgezeichnet und dabei „a bright flash […], like a firework exploding in the joint“ festgehalten. Bislang ist nur klar, dass das Knacken durch platzende Gas-Blasen verursacht wird, die wollen jetzt feststellen, ob die Blasen bereits vorher im Gelenk rumblubbern, oder erst durch die Gelenk-Überdehnung entstehen. However: Cameras ready, prepare for flash:

Ars Technica: Flash of a knuckle crack caught on video:

The video is from a new study from a team led by Robert Boutin, professor of radiology at the University of California, Davis. The researchers used ultrasound imaging to watch 400 knuckle pulls, 62 of which produced audible cracks. The bright bursts, like the one seen in the ultrasound above, corresponded to the audible cracks 94 percent of the time. But based on the timing, the source of the flash is not the source of the noise. Boutin told Ars that he doesn’t think the flash is a bubble pop either. “Although the bright flash appears suddenly, the bright—hyperechoic—area lingers,” he explained.