ACL Injuries diagram

What Is The Meniscus?

Each knee has two menisci. They are commonly called cartilages although this is not strictly accurate as they are made of a tough gristly material called fibrocartilage.

There is one meniscus on the inner side of the knee and another on the outer side. They are C or crescent-shaped and ‘cup’ the femur (thigh bone) as it sits on the tibia (shin bone).

What Does The Meniscus Do?

The menisci are important. Their main role is to spread the load being put through the two joint surfaces, thereby protecting the joint surface cartilage. In some ways they act as shock absorbers of the knee.

A torn meniscus does not function properly and it can lead to early wear in the joint.

Meniscal Cartilage Injuries

What Do The Menisci Look Like?

You can find out what the menisci look like in this video of a meniscal tear treatment.



What Happens When You Tear A Meniscus?

The commonest meniscus-related problem is a tear – a “torn cartilage”.

The symptoms of a torn cartilage can range from pain to clicking and catching sensations, through to complete locking of the knee.

A locked knee is caused by a large fragment of cartilage jamming in the knee joint, preventing you from fully straightening the knee.

A cartilage tear may also result in swelling or even a sensation of the knee giving way (though this is usually a sign of ligament damage).

Meniscal Cartilage tears & symptoms

How Do You Diagnose A Meniscal Tear?

Your Yorkshire Knee Clinic knee specialist will often diagnose a meniscal tear based on the history of injury.

In younger patients and adolescents there may be a very definite story of a twisting or jarring injury followed by swelling and clunking or locking of the knee. Rapid swelling indicates some bleeding into the knee joint.

If you have these symptoms you may be able to identify where in the knee the injury has occurred, literally putting your 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 meniscus cartilage goes from being tough and resilient to quite fragile and brittle. Therefore the cartilage tears or splits more easily.

Meniscal Cartilage tear on MRI scan

​In middle aged or elderly patients a cartilage tear may occur with a relatively minor injury. Rising from a chair, crouching down, standing from kneeling are all classic causes. 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. You may have felt a sharp pain during a run or other sport.

In this age group the swelling and pain is often less dramatic – you may not notice it for a few days.

Together with the history of the injury, an examination of the knee is a very useful aid to diagnosis.

We will usually take an x-ray. Even though the meniscus won’t show up, the x-ray will help eliminate 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 your knee surgeon will ask for an MRI scan 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 you are having. Even MRI can miss small tears.

MCL diagram of arthroscopic (keyhole) knee surgery

​How Do You Treat A Torn Meniscus?

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 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 often necessary. Larger tears usually require surgical treatment.

Any operation will nearly always be carried out via arthroscopic (keyhole) procedure.

Depending on the nature of the cartilage tear, it will either have to be repaired or trimmed to a smooth edge (a partial meniscectomy).

Meniscal Repair

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 for younger patients for a number of technical reasons. Over the age of 30, we know that the chance of a meniscus tear healing is reduced.

In some injuries the point where the meniscus is attached to the tibia (the meniscal root) can be pulled off. This is called a root avulsion and is important because, if it happens, the function of the meniscus is completely lost. It may be suitable for repair, depending on a number of factors which your surgeon will discuss with you.​


Meniscal Repair - meniscal cartilage-injury
Meniscal cyst diagram - Meniscal Cartilage Injury

Partial Meniscectomy

More commonly the torn part has to be removed in 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. Your knee surgeon will remove as little as possible, trying to leave a smooth stable edge of cartilage. The aim of this is to alleviate the meniscal symptoms.

Sometimes, a cleavage tear (a type of splitting tear within the substance of the cartilage usually found in older cartilages) can be associated with a meniscal cyst. This can be painful in itself and you may notice it as a small lump on the outside of the knee. Meniscal cysts are not dangerous.

Cysts on the outer side of the knee are more common than those on the inner aspect. 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.​


Meniscal Augmentation/Replacement

The meniscus cartilage is extremely important, especially in young patients, for protecting the joint surface against premature wear and arthritis.

So where a large part of the meniscus has to be removed, it is now possible to replace it with artificial or “donor” material.

Meniscal Augmentation

Augmentation is a relatively new technique, using a device to replace a missing piece of cartilage.

We don’t yet know how effective these devices will be in the long term, but there are some encouraging reports and the technology is evolving.

Meniscal Augmentation - replacement & implant - Meniscal Cartilage Injury
Healthy knee meniscal cartilage

Meniscal Transplant

Where there is little or none of the meniscus left behind, meniscal augmentation will not work. This is because we need a rim of the normal meniscus to stitch it toIn such cases a meniscal transplant may be appropriate.

This involves the transplant of donated tissue given by organ donors. The whole meniscus is stitched into place using a combination of keyhole surgery and small incisions.

Using a donor meniscus does not present the problem of tissue matching that you might have heard of, for example, with kidney transplants, but there are other risks. However, in certain cases, particularly young patients who have lost a whole meniscus, meniscal transplant is becoming a recognised option to address pain, although we do not yet know whether the treatment can slow down or prevent the development of arthritis.

It is important to be aware that meniscal transplant is relatively new and performed rarely – and the long term benefits are unproven – but it is a promising technique for some cases.

If You Are Experiencing Knee Pain, Swelling Or Locking,

Talk to an orthopaedic consultant at Yorkshire Knee Clinic. To book an appointment,

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