Researchers revealed information that may settle the mystery behind knuckle-cracking.

Scientists have been in disagreement over what causes a person to crack their knuckles. After more in-depth research using magnetic resonance imaging (MRI), they have come to some agreement, according to Reuters.

The conclusion was that cracking is caused by the rapid formation of a gas-filled cavity within a slippery substance called synovial fluid which lubricates the space between the finger bones. The cracking itself occurs in less than 310 milliseconds.

During the research, they also noticed a white flash occurring directly before the popping. They have concluded that this must be from the water rushing together.

“I quite like the sound, but that’s my inner nerd talking,” said Greg Kawchuk, a professor of rehabilitation medicine at the University of Alberta in Edmonton, Canada. Kawchuk led the study and published it in the scientific journal PLOS ONE.

The first time a study was done on knuckle-cracking was in 1947. The results from that study suggested that the sound from the action was from a formation of a gas cavity in the joint, which is clearly in-line with the most recent research.

Later, when the topic came under the microscope again, in 1971, scientists disagreed. From this study, researchers said that the collapse of a bubble inside the joint is what was triggering the popping sound.

During the most recent study, in order to capture the knuckle-cracking on the MRI, scientists had to literally pull on a man’s fingers. For the sake of science, co-author of the study, chiropractor Jerome Fryer, volunteered his knuckles for the research.

The procedure entailed each individual finger being put into a tube that was linked to a cable that was then pulled until the joints cracked.

“Rapid imaging with MRI was ideal for these studies because it allowed clear visualization of the bones and fluids surrounding them, and critically, the formation of the air cavity,” added University of Alberta biomedical engineering professor Richard Thompson.

“I personally do not like the cracking sound at all, I think primarily because I always imagined there was damage being done,” he added.

Many studies on the cracking of knuckles say that the action does no harm to the joint or hand. Kawchuk suggests that it is possible the cracking of a person’s joints could be healthy.