The Secret Behind the Sound of Knuckle Cracking

Scientists have uncovered the secret behind the sound that comes from cracking knuckles. They used ultrasound machines to settle years of debate regarding the source of this sound. According to Science Alert, Dr. Robert Boutin and a research team at the University of Davis in California conducted ultrasound imaging this summer on thirty healthy adults who regularly cracked their knuckles and ten who did not. The thirty individuals reported that they had been cracking their knuckles an average of twenty times a day for years. The researchers asked these forty participants to crack the first joints of their fingers while undergoing ultrasound imaging, collecting four hundred images and sounds. While researchers expected to see something around the bones of the finger joints that would lead to the 'pop' sound of knuckle cracking, they encountered something completely unexpected. Dr. Boutin told the Washington Post, 'We did not expect to encounter an explosion! What we observed was a bright spark as a result of the ultrasound. It was like an explosion in a fireworks display occurring in the finger joints. This was a completely unexpected finding for us.' The timing of seeing these sparks with the 'pop' sound was so high that researchers could predict the timing of the 'pop' sound from the images with about 94% accuracy. But what is the connection between this sound and the spark? Dr. Boutin states, 'Different theories have been formed over the years regarding the origin of this 'pop' sound. But now we can confidently say that this cracking sound and the bright spark observed in the ultrasound images relate to changes in the pressure of gases inside bubbles connected to the joints.' Although scientists still do not know whether the 'pop' sound is related to the formation of gas bubbles during knuckle cracking or their bursting, Dr. Boutin notes that further research is needed to answer this question. However, what is clear is that scientists have yet to find a reason for the harm of cracking knuckles. Contrary to popular belief, there is no scientific evidence that this action is harmful, and some specialists believe that it may even have benefits in increasing the range of motion of finger joints, although there is no scientific evidence to prove this.