The bone end surfaces of our articular joints are covered with a layer of cartilage which, thanks to its unique composition, allows for practically friction-free movement. This cartilage is known as “hyaline cartilage”.
Hyaline joint cartilage is unique in respect of its biomechanical properties. No material has yet been produced by humans to compare with joint cartilage in terms of stiffness, elasticity and friction. It is characterized by its high resistance to pressure and shock-absorbing properties. Hyaline joint cartilage consists largely of a matrix – a three-dimensional network of collagen fiber tissue, aggrecan and water. Only 1-3% of its volume is made up of cartilage cells.
Thanks to its structure, the matrix guarantees high stability under pressure and good elasticity, both at the same time. Much like a feather, when put under load, the cartilage responds by changing its shape, a shape to which it returns once the load is removed.
As the joint cartilage of an adult has no direct blood or nerve supply, it has only limited self-healing properties if damaged or subjected to change due to illness.
This can lead to major problems:
Joint cartilage can’t grow back
Injuries in the knee and ankle joints are increasingly common, caused by accidents, sporting injuries and overloading. For the reasons given above, joint cartilage has only a limited ability to regenerate itself following an injury. In most cases, the defect remains as a gap in the existing cartilaginous coating. Over the years, this becomes larger, until the cartilage of the entire joint is affected by the destruction.
In some cases, the body will attempt to heal the defect, although when it does so only low-grade replacement tissue will generally be produced. With major defects in particular, this scar tissue cannot compensate over time for the load placed on the joint and it is therefore quickly worn off again, with the result that discomfort generally resurfaces in a short space of time.
When this “shock absorber” is damaged, therefore, sooner or later the patient is likely to suffer from health effects such as pain, swelling and difficulty in movement. They can then expect to experience arthrosis and stiffening of the joints over time, possibly leading to a joint replacement operation.