The meniscus is a very important “shock absorber” of the knee. It is a semilunar shaped wedge made of a very strong substance called fibrocartilage. Except for the very most peripheral aspect there is very little blood supply. It serves several important functions. First, it protects the cartilage of the joint from wearing out and causing early arthritis. A large percentage of our body weight is distributed through the meniscus as we walk, run, and jump. Second, the meniscus adds to the stability of the knee joint by helping the shape of the femur or thigh bone conform to the tibia or leg bone. Finally, the meniscus also plays a role in the nourishment of the joint cartilage that covers the bones in the joint.
A ligament injury to the knee involves partial or complete damage to one of the major supporting ligaments. It can be as simple or minor as a stretching of the ligament resulting in some inflammation or as severe as a complete rupture causing instability of the knee. The ligaments are essential to proper knee function. There are four primary ligaments of the knee, two on the side – the lateral collateral ligament and the medial collateral ligament, and two in the center – the anterior cruciate ligament and the posterior cruciate ligament. They attach the femur or thigh bone to the tibia or leg bone. They are the primary stabilizers of the knee preventing abnormal motion of the femur relative to the tibia.
The bones of the knee joint like all other joints in the body are covered by hyaline cartilage. This is a remarkable substance which provides for a nearly frictionless surface for many decades. When the cartilage gets damaged, either by trauma, infection, or just long-term wear and tear, it results in osteoarthritis. There are other types of arthritis, but osteoarthritis is simply the result of the cartilage surface wearing out.