• So far there have been various theories about the origin of noise.
• Researchers observed the process in the magnetic resonance tomograph.
• There is no indication of whether the cracking is bad or good for the joints.

The cracking noise when pulling apart of fingers formed according to a study by the formation of a cavity in the joint.

Finger in the magnetic resonance tomograph

In the investigation, Greg Kawchuk’s team from the University of Alberta in Edmonton, Canada, took a closer look at a man’s metacarpophalangeal joints in an MRI scanner. The scientists present their results in the journal “PLOS ONE” .

Is there a threat to health?

Some people can crack their joints when they pull their fingers apart. There is currently no evidence as to whether this phenomenon is bad or good for the joints. “So far, no one has ever been able to prove that this  cracking is harmful to health in the long term,” says Professor Jörg van Schoonhoven from the Clinic for Hand Surgery at the Rhön Clinic in Bad Neustadt an der Saale.

Different theories

For a long time there have been various theories about where the popping sound when clicking your fingers comes from. Some scientists suspected that the crackling sound was caused by a bursting bubble in the joint space.

Other researchers hypothesized that the sound is caused by the flapping of ligaments.

Another explanation for the origin of the cracking is what is known as tribonucleation: a mechanism in which the movement of surfaces creates gas bubbles in a liquid.

Study author as guinea pig

To date, there has not been any direct experimental evidence that solidly supports any of the theories. Kawchuk’s researchers wanted to change that. 

For their study, the scientists needed someone who had the ability to crack their metatarsophalangeal joints on request. These joints connect the bones of the metacarpus to the base members of the fingers. The choice fell on Jerome Fryer, one of the study authors.

Pull until it cracks

In the experiment, the researchers examined each finger of the test subject in isolation in a special magnetic resonance tomograph, with which movement sequences can be recorded.

The finger was attached to a kind of tube that was connected to a cable at the other end. Then the cord was pulled until Fryer’s fingers cracked. The entire process in the joint was recorded with an MRI scanner.

Is a cavity the cause?

Shortly before the cracking could be heard, the researchers were able to observe the formation of a cavity in the images.

The scientists therefore assume that tribonucleation has taken place in the joint: “It is a bit as if a vacuum is being formed,” explains Kawchuk in a communication on the study. “If the joint surfaces suddenly separate, there is no longer any liquid left to fill the increasing joint volume. This creates a cavity.” The noise is generated by this event. 

“It is interesting to know what acoustic phenomenon is behind the cracking of the fingers,” said the hand surgeon van Schoonhoven. However, by including only one person in their study, Kawchuk’s researchers would be able to explain the phenomenon only for that person. “The experimental setup does not allow any generalized statements,” said van Schoonhoven.

• Osteoarthritis results from wear and tear on bones and joint capsules.
• Five million Germans suffer from the consequences.
• Briefly explained: which osteoarthritis treatment helps whom?

If the joints hurt, it is usually osteoarthritis : it is the most common of all joint diseases. About five million Germans suffer from it. Osteoarthritis occurs when bones, ligaments, tendons and joint capsules wear out.

This is important to differentiate the disease from rheumatoid arthritis. Inflammation is the cause here.

This is important for osteoarthritis treatment

“Arthrosis is a disease that runs in waves,” explains Johannes Flechtenmacher, President of the Professional Association of Orthopedists and Trauma Surgeons. Less painful phases alternate with those that torment those affected.

The aim of the treatment is to relieve the pain on the one hand and to maintain or restore the ability to move on the other.

Osteoarthritis needs combination treatments

Ideally, the doctor combines non-drug treatments such as physiotherapy, nutritional recommendations, and hot or cold applications with medication. These are mainly used in the acute pain phase.

“In the less painful episodes, patients should try to avoid medication,” explains Flechtenmacher. In principle, movement in particular is an important component of therapy. His motto: “Move a lot, load little.”

Five osteoarthritis treatments put to the test:

1. NSAIDs: cortisone-free pain relievers

This is how the drug works: The non-steroidal anti-inflammatory drugs (NSAIDs) are the classic all-rounders in pain relief. They have both anti-inflammatory and analgesic effects, but do not contain cortisone.

Medicines include ibuprofen, diclofenac, or naproxen. They block two important enzymes that play a role in the sensation of pain: Cyclooxygenase (COX) isoenzymes I and II.

The so-called Cox II inhibitors are therefore well suited to treat acute joint pain associated with osteoarthritis.

NSAIDs also have an antipyretic effect.

Side effects: Gastrointestinal complaints and an increased risk of cardiovascular diseases are among the risks of NSAIDs. “That is why it is particularly important to tailor the osteoarthritis treatment to the patient,” explains orthopedist Flechtenmacher.

For example, ibuprofen is not suitable for patients with kidney problems, and diclofenac hits the liver. Both drugs also have a negative effect on the cardiovascular system. Naproxin is therefore better suited for heart disease patients with osteoarthritis.

2. Opioids

This is how the drug works: Opioids are effective remedies that are used against severe joint pain. By attacking the opioid receptors, they prevent pain from developing and being transmitted.

Tramadol is one of the morphine-like drugs. “Morphines are not suitable for treating acute phases of pain in osteoarthritis,” says Flechtenmacher. This is especially true for plasters. Morphine should only be used for chronic treatment if no other therapy is helping the patient.

Side effects: Many sufferers suffer from the exhaustion caused by morphine. Especially in older people, opioids aggravate many age problems. These include, for example, constipation and dizziness. This also increases the risk of frail patients falling.

3. Hyaluronic acid

In addition to drugs that directly combat pain, there are active ingredients that intervene in the mechanism of the disease. A typical representative is hyluronic acid.

This is how the drug works: Doctors inject hyaluronic acid into the joint to treat osteoarthritis. That’s the only way it works. “In contrast, it is pointless in tablet form, as is sometimes offered,” explains Flechtenmacher. Only in the joint does the drug help the knees or fingers move more smoothly.

With regard to evidence-based studies, hyaluronic acid should be viewed critically, adds the doctor. For example, the relief of osteoarthritis on knock knees or bow legs, where it is biomechanically induced, works less well than on straight legs.

Side effects: As a rule, osteoarthritis patients tolerate hyaluronic acid very well. Since it is injected directly into the joint, there is the usual risk of infection from the method.

4. Natural medicine

This is how the treatment works: Natural active ingredients such as nettle leaves, willow bark or devil’s claw should also relieve pain. The latter contains, among other things, harpagoside. Similar to the non-steroidal anti-inflammatory drugs, they are supposed to inhibit the formation of the pain messenger prostaglandin.

“So far, however, nothing has been identified in evidence-based studies that proves the effectiveness of the natural active ingredients,” explains Flechtenmacher.

Side effects: They are dependent on the natural medicine product. The instruction leaflet of the devil’s claw, for example, warns of possible gastrointestinal complaints such as diarrhea, nausea, flatulence, vomiting as well as dizziness and headaches or rashes.

5. Acupuncture

This is how the treatment works: As with natural active ingredients, evidence of how acupuncture works for osteoarthritis has not yet been provided in scientific studies.

On the contrary. An Australian study looked at the effects of acupuncture. The results published in the “JAMA” magazine showed: Acupuncture with needles or laser has no relevant effect on pain and function in patients over 50 with knee osteoarthritis and moderate or severe chronic pain.

However, acupuncture helps some osteoarthritis sufferers. Johannes Flechtenmacher, for example, relies on the alternative form of treatment

• light and irregular pain
• when many illnesses in the affected person rule out other drugs.

In addition, there are many patients who benefit from the doctor’s attention and empathy alone.

Side effects: The symptoms can get worse at first, writes the German Pain Society on acupuncture . And adds: “Occasionally there are slight bruises or bruises, and brief circulatory reactions can also occur during acupuncture treatment.”

In any case, those affected should not treat their joint pain independently, but should always have it checked out by a specialist.