Meniscus Overview

The menisci are comprised of tough, rubbery, fibrous tissue and are located in the knee joint between the femur and the tibia.  The menisci conform to the surfaces of the bones upon which they rest, with the medial meniscus on the inside of the knee, and the lateral meniscus resting on the outside of the knee.  The “C” shape and wedged profile of each meniscus help maintain stability in the joint.

The medial meniscus and lateral meniscus have multiple functions.  First, they act as shock absorbers for the knee, lowering the stress to the articular cartilage in the joint and helping to prevent or delay degenerative arthritis.  Another function of these structures is to help distribute weight and improve knee joint stability.  Finally, by acting as spacers between two main bones in the knee (the femur and the tibia) the menisci prevent friction between the bones and help distribute normal joint fluid into the articular cartilage.  If there is no meniscus in the knee, body weight is unevenly applied to the leg bones, causing excessive forces in specific areas and leading to arthritis.  

Nourishment is provided to each meniscus by small blood vessels, although there is a large area in the center of the structure which has no direct blood supply.  The absence of blood supply to this region means it is difficult to heal following a meniscus injury.

The meniscus is often described by three zones:  the front third is known as the anterior horn, the back third is the posterior horn, and the middle section is the body of the meniscus.

There are several differences between the medial and lateral meniscus, both anatomically (how they look) and functionally (how they work).  Since the medial meniscus is attached to the joint capsule all around its outer edge, it does not slide much in any direction and is therefore more likely to tear.  The lateral meniscus is more rounded, and there is a section where it is not attached to the joint capsule wall.  Therefore it is more likely to move rather than tear.