October 28, 2021

Mystery solved: Why do knuckles crack?

Knuckle popping and cracking is a fairly polarising habit, but it turns out that the science behind what produces the sound has also put people at odds.

Researchers have been developing, testing, and debating theories since at least the late 1930s, but a team from Canada has finally settled the matter once and for all.

They did so using a skilled subject, a custom built finger-pulling device, and an MRI.

The fingers of the test participant, who was described as the Wayne Gretzky of knuckle cracking, were yanked.

As the joints were being jarred, the imaging machine recorded what was going on inside of them at the various stages of movement.

The methodology and the results were similar to those of a study performed in 1947, in which x-rays were taken as a person’s fingers were pulled.

In both cases, it was determined that the sound occurs as a result of a cavity suddenly forming within the knuckle’s lubricating fluids.

The team is hoping to perform the study again, but next time with more participants of varying knuckle-cracking skills.

Their goal is to gain further insights that may be useful for assessing joint health.