Cartilage function
The knee joint is made up of three major bones: the thigh-bone (femur), the shin-bone (tibia) and the kneecap (patella). The meniscus on the inside and the outside of the knee acts as a spacer between the upper leg and the shin-bone, equally distributing the pressure on the lower leg. The extremities of the bones that make up the knee joint are covered with a thin layer of cartilage.
Cartilage ensures supple knee movements and forms an indispensable part of the knee joint. Joint cartilage is a thin, elastic tissue that protects the bone and makes certain that the joint surfaces can slide easily over each other. A change in the shape, structure or volume of the cartilage may cause any pressure on the knee joint to be painful.
There are two types of joint cartilage in the knees: fibrous cartilage (the meniscus) and hyaline cartilage. Fibrous cartilage has tensile strength and can resist pressure. Hyaline cartilage covers the surface along which the joints move. It is white and transparent, like porcelain, and gives a similar resistance to an elastic band when pushed. Although it is scarcely five millimeters thick, it is very sturdy and can resist pressures of up to seven times the body’s own weight. The fibers which make up the cartilage tissue form various layers, which each have their own specific function.
Unfortunately, cartilage will wear - not just over the years, but also as a result of mechanical stress. Additionally, cartilage has a very limited capacity for self-restoration. Moreover, the newly formed tissue will generally consist for a large part of fibrous cartilage of a lesser quality than the original hyaline cartilage. As a result, new cracks and tears will form in the cartilage over time.
The reason why cartilage has only a small capacity for self-restoration, and what makes it very unique, is that it does not contain any blood vessels unlike all other tissues in the body. The necessary nutrients are derived exclusively from the liquid in the joint capsule.
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