|
|
 |
 |
« A diagram of knee anatomy »
Related topic >
Knee anatomy
Each knee has two menisci. They are commonly called “the cartilages”,
although this is not strictly accurate. There is one on the medial
(inner) side of the knee and one on the lateral (outer) side of the
knee. They are C or crescent shaped and serve to cup the femur as
it sits on the tibia to improve the congruity of the joint. In some
ways they act as shock absorbers of the knee. They are made up of
a tough gristly material called fibrocartilage.
« A diagram of a normal meniscus »
« An arthroscopic view of a normal meniscus
»
« An MRI scan showing a normal meniscus
»
The commonest problem which arises with a meniscus is a tear. Occasionally
the problem can be related to a cyst on the side of the meniscus.
The symptoms from a torn cartilage can range from pain, to clicking
and catching sensations, through to complete locking of the knee.
A locked knee arises when a large fragment of cartilage jams in the
front of the knee, resulting in an inability to fully straighten the
knee. Other associated features of a cartilage tear may be swelling
or even a sensation of giving way (though this is usually a sign of
ligament damage).
« A diagram of a longitudinal tear »
« A diagram of a bucket handle tear »
« An arthroscopic view of a bucket handle
tear »
« A diagram of a radial tear »
« An arthroscopic view of a flap tear »
The diagnosis of a meniscal tear is often made on the history of injury.
In the younger adult patient or adolescent there may be a very definite
story of a twisting or jarring injury followed by swelling and clunking
or locking of the knee. These symptoms are often very well localised
and the patient may be able to put his finger on one side of the knee
or the other according to which cartilage is torn.
Sometimes cartilage tears are associated with other injuries such
as ligament ruptures.
A tear of the meniscal cartilage in a young adult usually occurs with
a greater force than in a middle aged or elderly person. The reason
for this is that the strength of the cartilage reduces as you grow
older. With the natural aging process, the nature of the meniscus
cartilage goes from being a very resilient rubbery composition to
becoming more brittle and degenerate.
Therefore, in a middle aged or elderly patient a cartilage tear may
occur with a relatively minor injury such as rising from a chair,
or a minor twisting episode. Indeed sometimes it is difficult for
the patient to recall the exact moment at which the cartilage tear
occurred, but recent vigorous activity may be relevant e.g. going
on a long walk, moving furniture.
The examination of the knee along with the history is a very useful
aid to diagnosis.
An x-ray will usually be undertaken even though a cartilage will not
show up. This is because it is a simple investigation which can exclude
other problems such as arthritis, an injury to the bone, or loose
bodies (fragments of bone) in the knee; any of which can mimic the
symptoms of a cartilage tear.
Sometimes an MRI scan will be performed to confirm a cartilage tear
if there are any doubts. An MRI scan is not always used and will depend
on the clinical diagnosis and problems that the patient is having.
Even MRI can miss small tears.
Once the diagnosis of a torn meniscus is made you may well require
surgery to treat it, as it is uncommon for these tears to heal. This
is because in order for something to heal, it requires a blood supply
and the meniscus itself has a poor blood supply.
Symptoms from small tears can settle down, however, over about 6 weeks.
If symptoms last longer than this, surgery is usually necessary.
Surgery will nearly always take the form of an arthroscopic (keyhole)
procedure, called an arthroscopy.
Depending on the nature of the cartilage tear, it will either have
to be repaired, or trimmed to a smooth edge ( a partial meniscectomy
).
« A diagram of arthroscopic meniscectomy
»
A small proportion of meniscal tears are suitable for repair. If a
tear is treated soon after it occurs and the tear itself lies in the
outer part of the meniscus, where there are tiny blood vessels, it
may be suitable for repair with special sutures or anchors. In general
this is only considered in the relatively younger age group for a
number of technical reasons.
« A diagram of a sutured tear »
More commonly the torn part has to be removed, a partial meniscectomy.
This is done using special small punches and cutters via one of the
portals (keyhole incisions) at arthroscopy. The amount of cartilage
removed depends on the size of the tear. As little as possible will
usually be taken out, trying to leave a smooth stable edge of cartilage
which will not cause you any further symptoms.
Sometimes, as noted previously, a cleavage tear (a type of splitting
tear within the substance of the cartilage usually found in degenerate
cartilages) can be associated with a meniscal cyst. This can be painful
in itself and may present as a small lump on the outside of the knee.
Cysts on the outer (lateral) side of the knee are more common than
those on the inner (medial) aspect of the knee. Usually these cysts
can be drained into the knee at the time of meniscectomy. Rarely,
they may require removal with a bigger cut through the skin directly
over the swelling.
« A diagram of a meniscal cyst »
> Back to top |
|
|
|
