Osteoarthritis danger? Why our finger joints sometimes crack

What really makes our fingers crack

Crackling fingers are a true horror for many people. With some, the sound even causes goose bumps. It is said in the vernacular that this also causes arthritis. However, there is no proof for that. But what makes our fingers crack? There is now a new theory.

Experts have been arguing about the causes for decades

For a long time people have been arguing about the causes of finger-biting in the professional world. In 2015, an international team of researchers led by senior author Professor Professor Greg Kawchuk from the Department of Rehabilitation Medicine at the University of Alberta, Canada, published in the journal "PLOS ONE" the results of a study that found that cracking was triggered by scientists , Now other experts reject the thesis of that time.

A few years ago, a study was published that showed what causes the cracking of the fingers. Now, researchers have doubts about the thesis and claim that another cause is responsible. (Image: Astrid Gast / fotolia.com)

The joints crack

For decades, researchers have been wondering what makes our fingers crack. There is agreement that it is the joints that crack - and that you have to pull them apart.

Two British scientists from St Thomas' s Hospital Medical School in London in 1947 found on x-ray images that a gas bubble had formed in the gap between the joints.

In an article published at the time, they reported that, in their opinion, this led to the sound.

In the early 1970s, however, researchers from the University of Leeds (United Kingdom) claimed in a technical paper that not the formation of the bubble, but their bursting the sound care.

Cavity in the joint

However, in 2015, a knock-out theory setback emerged when scientists around Professor Kawchuk of the University of Alberta used MRI scans to observe for the first time how a traction force in the joint rapidly forms a cavity that causes the fingers to snap.

The surrounding of the joint capsule articular surfaces (ends of the bones) are therefore separated by a gap, which is filled with viscous synovial fluid.

When pulled on the finger, this gap widens significantly and suddenly there is a cavity in the synovial fluid, which is connected to the clicking sound.

Fingerknacken observed on MRI

For their investigations, the researchers first needed someone who could crack their ten fingers at will.

Fortunately, a colleague who had this ability was found in their ranks and they pushed this, lying on his stomach and with his finger first in the MRI tube.

At the tip of his finger, they attached a pulling device, which allowed a clear view of the joint during the following shots. They then pulled on the explorer's finger until the crackling sound was heard.

The MRT recorded the events in 3.2 frames per second, so that a film was created, on which the process could be followed exactly.

At low tensile forces, according to the researchers initially no changes in the joint could be found, but was pulled sufficiently strong on the finger, widened the joint space and it was very sudden a gas-filled cavity in the synovial fluid (synovial fluid).

Formation of a vacuum in the joint

"It's a bit as if a vacuum is building," Professor Kawchuk said in a press release from the University of Alberta.

As the interfaces separate at once, there is insufficient fluid available to fill the increasing volume, creating a void.

This event was based on the MRI scans unequivocally attributable to the emergence of the crack, while the regression of the bladder after releasing the finger was noiseless.

Thus, the researchers have confirmed the original thesis of the British scientists in 1947 and refuted subsequent, different study results.

New theory

But now doubts come up again. Because the two theoreticians V. Chandran Suja, who researches at the University of Stanford (USA), and his French colleague A.I Barakat (CNRS Palaiseau), examined the hypothesis of Canadian researchers using mathematical model calculations.

They recently published their findings in the journal "Scientific Reports".

According to the scientists, the complete or even partial imploding and not the emergence of the bubble can cause cracking. So it may well be that in future further theses on the true causes of finger-bruising will be established. (fp, ad)