YOUR KNEE AND HOW IT WORKS: CARTILAGE
The basic function of cartilage is to absorb shock and protect the bones. There are two types of cartilage in the knee joint: articular cartilage and the menisci.
The articular cartilage, also known as hyaline cartilage, is a white elastic material that lines the three bones that form the knee joint: the patella, femur and tibia. It is anywhere from 1/8 to 1/2 inch in thickness. Articular cartilage allows the knee (and other joints) to move in a fluid motion. Articular cartilage is composed primarily of water, collagen, and substances called proteoglycans, which are made up of large proteins and sugars. The wearing away of the articular cartilage, either through a traumatic injury or overuse, can result in arthritis. Softening or wearing away of the articular cartilage is called chondromalacia. Severe arthritis becomes evident when the hyaline cartilage is completely worn exposing raw bone (the subchondral bone).
Each knee has two menisci: the medial mensicus and lateral meniscus. (Medial refers to a part that is closest to the other leg, lateral refers to a part that is further away from the other leg.) The menisci are made of fibrous cartilage, a thick rubbery-type substance. Located on top of the tibial plateau, both menisci are basically shock absorbers, helping the knee withstand the enormous shear (side) forces that are placed on it daily. Meniscal injuries are fairly common, especially among athletes and are often a result of excessive force. Wear and tear due to age can also cause damage to the menisci.
healthy bones Osteoporosis Rheumatic