Meniscal Cartilage Injuries
A diagram of knee anatomy A basic understanding of Knee anatomy can be obtained here. BackgroundEach 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.
Symptoms of Meniscal InjuryThe 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).
DiagnosisThe 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. Treatment of a torn meniscusOnce 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 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.
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.
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