Injured cartilage cannot heal itself July 22, 2016, 11:03

The study may be hugely significant for the treatment of osteoarthritis, which is one of the most widespread common diseases and the most common musculoskeletal system disease. More than half of all Danes above 40 years of age and every Dane above 60 years of age suffer osteoarthritis in one or several joints.

«We wanted to assess, once and for all, the body’s ability to heal cartilage injuries. And so we examined the exchange of the main properties in the cartilage to locate possible changes in connection with disease. The study revealed that the cartilage’s ability to heal itself stops in adulthood regardless of disease or injury. Treating large patient groups with osteoarthritis or joint injuries caused by sports has long proved a medical challenge, however, this new result helps us arrange more efficient treatments," says Clinical Professor Michael Kjær from the Department of Clinical Medicine at Bispebjerg Hospital.

Articular cartilage is the body’s weak link
Researchers from the University of Copenhagen and Aarhus University conducted the research, which involved 23 subjects from all age groups, including 15 individuals with healthy cartilage and 8 individuals with osteoarthritis. The scan results revealed that the formation of proteins and molecules in the cartilage stops once the bones are fully developed, around the age of 15–16, after which it maintains its structure without regenerating either tissue or cartilage.

This is because the body no longer produces new collagen for the supporting structures in the cartilage. Collagen is Latin for «glue» and it ensures the cartilage’s cohesiveness and elasticity. However, when tissue and cartilage is worn down by osteoarthritis or injury, the cartilage loses its shock absorbing quality, which in turn means that bones and joints start colliding and scarfing.

«In fact, we may not be ‘designed’ to last beyond 40 years of age. Evolutionarily, the body’s joints haven’t kept up with our increased life expectancy, and the extra years may actually wear down our joints. However, there are solutions that’ll enable us to maintain our mobility, by way of, for example, the right type of exercise," Michael Kjær explains.

Prevention and exercise is key
The study’s results provide a challenge for experimental treatments such as cartilage transplantations, collagen supplements and stem cell treatments, and if the cartilage is sufficiently worn down there is only one long-term solution: joint replacement surgery. However, according to Michael Kjær, it is possible to prevent wear and tear as well as injuries through exercise and diet.

«Optimally, we should prevent injuries from childhood and teenage years and possibly also examine whether we are prone to cartilage injuries later in life. However, once the damage is done, you can, by way of gentle exercise, train other molecules in the cartilage to absorb fluids, which in turn will increase the remaining cartilage’s elasticity and shock absorption. Generally speaking though, we should stay active throughout life and avoid too much wear and tear in our joints," Michael Kjær concludes.

Summary
The cartilage in our joints contains the protein collagen, which is produced as our skeleton develops through childhood and teenage years. However, when we reach 15–16 years of age, both bones and cartilage are fully developed and the collagen production no longer leads to the replacement or build-up of cartilage. Subsequently, worn down cartilage, due to sports injuries or osteoarthritis, cannot be regenerated. Which is why it is important to prevent injuries from childhood and to stay active throughout life without damaging the cartilage by way of severe strain and hard landings after a jump, for example.

Weight training and endurance training such as cycling, Nordic walking or rowing can activate and strengthen the cartilage molecules’ ability to absorb fluids. The molecules are located in a so-called collagen matrix, constructed by what looks like arching ropes or wires in both tissue and cartilage. In between these arches there are a number of molecules that are able to absorb and bind fluids. Once the joints are activated through training, the molecules learn to absorb fluid, by way of osmosis, which in turn stimulates the remaining cartilage.

If the cartilage construction is terribly worn down, this is no longer possible and the only solution is joint replacement surgery.

The study does not reveal why some people are more prone to cartilage injuries than others. Generally speaking, however, damages to the cartilage can increase the risk of developing osteoarthritis, which is why focusing on preventive measures in future treatments of sports injuries and the wearing down of cartilage in connection with osteoarthritis is decisive.

Michael Kjær — Professor and DMSc at the Department of Clinical Medicine and the Centre for Healthy Ageing

Michael Kjær conducts research on how exercise and physical activities affect the organism. He heads a large research group focusing on, among other things, sports injuries and what happens to injured tissue as well as the development of the musculoskeletal system as we age.