• The body’s own stem cells have a positive effect on osteoarthritis-related inflammation in the knee.
• A study now wants to clarify whether they actually build up permanent cartilage.
• A transplant can repair minor cartilage damage in young patients.

After a certain age, signs of wear and tear become noticeable in the knee . After the age of 30, the risk increases linearly. The painful, inflammatory breakdown of cartilage in the operating room and with an artificial knee ends 150,000 times a year. Then smooth metal has to replace the cartilage layer, which allows round, painless movements in a healthy knee.

The idea frightens many people suffering from osteoarthritis. They hope for new methods to rebuild lost cartilage: stem cells should help.

Belly fat provides the best stem cell material

The doctor uses the patient’s belly fat as a starting material. The idea behind it: stem cells can be obtained particularly easily and in relatively large numbers from vascular fat tissue. Injected at the location of the defect, they learn from the microenvironment into which cell type they should develop.

According to this principle, the doctor and stem cell researcher Eckhard Alt uses the undifferentiated cells : Stem cells from the patient’s fat tissue are processed in the operating room within an hour and injected into the patient where he needs them – for example into the osteoarthritis knee.

The founder of the “Interdisciplinary Stem Cells Research Center” in Houston and a private clinic in Munich sees stem cells as the future therapy for chronic inflammatory diseases of the musculoskeletal system – among other things.

The cell extract in the knee does not guarantee success

Some orthopedic practices that offer the procedure honestly state that it is a not generally recognized attempt at healing with no guarantee of success. Rather, it is a final experimental attempt to remedy knee problems without a joint replacement.

“In this so-called ‘point-of-care’ application, a cell extract is injected that not only consists of stem cells,” explains Oliver Pullig from the Fraunhofer Translational Center for Regenerative Medicine in Würzburg. How many stem cells that are supposed to develop into cartilage material actually get into the knee is just as little regulated as the preparation of the suctioned off belly fat.

Stem cells instead of knee prostheses

A Europe-wide study is currently looking for scientific evidence of the anti-osteoarthritis potential of the body’s own stem cells.

A small one with six patients in Würzburg and twelve in Montpellier, France, led to success in 2013: Almost all participants canceled their previously unavoidable operation for a knee prosthesis. “Your complaints had improved throughout,” explains Oliver Pullig. “A reconstruction of cartilage was unlikely with such a large damage.”

The follow-up study that has just begun with 153 participants at ten European locations therefore fulfills a requirement that the German study director Ulrich Nöth from the Evangelical Forest Hospital Berlin-Spandau formulated back then: Stem cell therapy is best suited for patients with middle and middle-aged osteoarthritis. You are no longer eligible for a cartilage transplant, but you are too young to have an artificial joint.

New cartilage from stem cells? A study should show it

Like the pilot study, the ADIPOA2 study uses so-called mesenchymal stem cells from the abdominal fat of each subject. These precursor cells of the connective tissue have the ability to develop into cartilage, bone or fat cells.

Biologist Oliver Pullig explains: “We take 100 milliliters of belly fat from each participant. The stem cells obtained from this are multiplied millions of times in special laboratories. That takes a good two weeks. 51 patients then receive two million of these pure stem cells injected into the joint, 51 patients receive an injection with 10 million cells and 51 patients receive a placebo. “

Results should be available by the end of 2018, and thus scientific proof of whether stem cells fulfill the hope of permanently building cartilage. The scientist is optimistic: “If successful, the therapy with stem cells as a drug could be ready for the market at the next study level. It doesn’t take five years. “

Cartilage transplant only helps to a limited extent

Another method to restore lost cartilage is transplantation, which has been tried and tested for 20 years. So far, however, it has only been successful in the case of centimeter damage in an otherwise intact knee. The operation is laborious and the healing process long.

In the first keyhole surgery, the doctor removes a small piece of healthy cartilage, hardly larger than a grain of rice. These cartilage cells are propagated in the laboratory in three to four weeks. In a second operation, the surgeon places these cells or the cartilage patch on the defective area in the knee.

After that, the knee must not be subjected to any load for six weeks, then only lightly for another six weeks. Only after a year is the joint stable enough for sport to be possible.

Cartilage from the laboratory is expensive

The transplant is only suitable for younger knee patients whose cartilage and joints are free from osteoarthritis. If this therapy is successful, it can prevent further cartilage damage and a later threatened knee prosthesis.

Then, in the long term, the costs of several thousand euros for cells grown in a laboratory will pay off.

Hyaluronic acid can at least relieve pain

If these methods are out of the question, another remedy can help: synthetic hyaluronic acid is often misunderstood as a substance for building up cartilage. However, it cannot produce worn cartilage, but serves as a lubricant and for joint care.

Orthopedic surgeons inject the moisture-retaining gel three to five times at weekly intervals. Hyaluronic acid relieves pain and promotes mobility – permanently for some patients, at least for a year or two for others. Then the treatment can be repeated.

• 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.