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Meniscal tears

The menisci are half-moon shaped and act as shock absorbers. They are made up of a different type of cartilage  to the joint surface (articular) cartilage. Each knee has an inner or medial meniscus and an outer or lateral meniscus. The menisci sit between the thigh bone (femur) and the shin bone (tibia). They distribute the forces across the knee and allow the bones to glide smoothly on one other without friction. They also provide stability to the knee.


The menisci are either damaged as a result of a traumatic injury or as the result of wear and tear. The most common way to tear the meniscus is by a twisting motion on a bent knee. This may occur in combination with a ligament injury. 60% of patients who tear their anterior cruciate ligament (ACL) also damage one or both of their menisci at the same time. This is referred to as a traumatic meniscal tear. The more common, degenerative type of tear, can occur with very simple activity such as bending down to pick something up or with simple stair climbing.

 

Normal Meniscus
Normal Meniscus

Intra-operative picture showing a normal inner/medial meniscus in the centre of the knee joint.

Torn Meniscus
Torn Meniscus - Meniscal Tear

Intra-operative picture showing torn inner/medial meniscus sitting out of position in the centre of the knee joint.



Following a meniscal tear, a patient experiences pain (which is localised to the side of the knee joint where the tear has occurred). It is far more common to tear the inner or medial meniscus than the outer meniscus. Patients often point to the exact location of the tear, and they say "it hurts here!". Symptoms associated with this are pain, swelling, clicking and difficulty with walking or bending activity. If the tear is severe and a large fragment of the meniscus flips into the centre of the knee joint it may lead to "locking" and an inability to move the knee which effectively gets stuck. Although the medial/inner meniscus is more commonly injured tears of the lateral/outer meniscus are more significant.

 

The diagnosis of a meniscal tear involves an appropriate history from the patient, together with a clinical examination. An MRI scan may be useful to help both confirm the diagnosis and to determine what type of tear has occurred.

 

Loss of the meniscal shock absorber tissue leads to uneven weight distribution and excessive  force passing from one joint surface to the other within the knee. This leads to arthritis or wear and tear. Most meniscal tears require key-hole surgery. It is sometimes possible to repair a torn meniscus. Meniscal repair is a complex procedure and is best carried out by an experienced knee specialist. The results of meniscal repair surgery, even in the best hands, are 65% success for an isolated tear and 80% where there is an associated ligament rupture within the knee. If repair is not possible, then simple debridement of the tear is carried out to remove the damaged fragment and preserve as much of the meniscal tissue as possible and thereby retain its shock-absorbing function.

 

Orthopaedic consultation

Orthopaedic consultation

Key-hole  knee surgery

Key-hole knee surgery

Mr Wilson carrying out knee arthroscopy surgery

Mr Wilson carrying out knee arthroscopy surgery

Anaesthetist - Dr Nick J looking over the drapes

Anaesthetist - Dr Nick J looking over the drapes

Scrub team before ACL surgery

Scrub team before ACL surgery

Mr Wilson examining a patient's knee

Mr Wilson examining a patient's knee