The Knee Joint
The knee joint is the largest and most heavily loaded joint in
the body. It connects the upper leg with the lower leg and
transfers the entire weight of the body to the lower leg.
Especially during sports activities involving rotational and
transverse movements, strong forces act on the knee joint. This
often leads to excessive strain and painful injury to the knee
structures,in particular the cruciate ligaments, cartilage
surfaces, and menisci. Very often there is combined ligament and
meniscus damage. Given that this type of injury leads to an
unstable knee and excessive wear and tear of the joint, the
earliest possible surgical stabilization is essential.
What is the Function of the Meniscus?
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
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
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.
An undamaged meniscus is key to a fully functioning knee.
However, this fact has only been really understood in the last 20
years. Prior to this realization a damaged meniscus was often
simply removed. Although patients initially did quite well
after this procedure, they later often developed osteoarthritis or
other knee problems.
Today treatment varies depending on the extent and location of
the meniscus tear. For a minor tear, when pain and other
symptoms go away on their own, muscle strengthening exercises may
be all that is recommended. The doctor may advise working with a
physical therapist to make sure exercises are done properly.