Meniscuses are small C-shaped tough cartilages that sit between the femur (thigh bone) and the tibia (shin bone). Both ends of these bones are covered with articular cartilage (joint surfaces). Meniscuses provide a rubbery shock absorber between the bone cartilages. The term "torn cartilage" refers to meniscal cartilage. ANATOMY

The medial meniscus is more commonly injured because it is firmly attached to the medial collateral ligament and joint capsule. The lateral meniscus, located on the outside of the knee is more mobile.

Damage to the menisci (images)can occur at any age and during practically any form of activity. There are two categories of meniscal injuries: acute tears and degenerative tears:

Acute tear usually occurs when the knee is bent and forcefully twisted, while the leg is in a weight bearing position. It is a frequent injury in sports but it may happen in daily life.

In older patients, both bone cartilage and meniscus cartilage get more brittle and the meniscal tear must be related to degenerative processes. As the meniscus ages, it weakens and becomes less elastic. Degenerative tears may result from minor events and there may or may not be any symptoms present.

Pain is the main symptom. Pain is felt along the inside or outside aspect of the knee depending on which cartilage has been torn. Pain can appear progressively or suddenly. It is often intermittent and exacerbated by any twisting of the knee. Swelling is possible. Locking of the knee is not frequent (inability to fully straighten the leg). A sense of giving way within the knee is possible.

The diagnosis is brought up by clinical examination: the knee is tender when pressed on the joint line (where the tibia and femur meet) of the injured side. It will be confirmed by a magnetic resonance imaging (RMI). The X-rays are useless for the diagnostic of soft tissues lesion but useful for assessment of associated osteoarthritis.

The MRI assesses the type of the meniscus lesion: location (tears in the outer third have the best chance of healing), pattern, completeness and stability (a stable tear does not move and may heal on its own. An unstable tear allows the meniscus to move abnormally and is likely to be a problem if it is not surgically corrected.

There is no medical need for surgery but the patient will elect to do surgery if he is too disabled.

In the 1970s, there was no arthroscopy and it was common to remove a damaged meniscus entirely. This led to early degenerative arthritis in many patients. Nowadays, arthroscopy allows to only remove the torn part of the meniscus (menisectomy) or to try to repair it.

Meniscal repairs are only performed in young people on tears near the outer third of the meniscus where a good blood supply exists or on large tears that would require a near-total resection. The torn portion of the meniscus is repaired by using sutures that join the torn edges of the meniscus so they can heal. Full weight bearing (crutches) is not permitted for 3 to 6 weeks after surgery, depending on the type of repair. If the meniscus does not heal (persistent pain, mechanical symptoms), its removal may be necessary.

Partial menisectomy arthroscopy is curative of the meniscal pain in acute tears. Return to activities can start 4 to 6 weeks following surgery.

But knee pain may persist if associated to chondropathy (especially patella chondropathy). That is why it is important to look for frequent anterior patella pain associated symptoms before surgery. The patella pain will not be cured by arthroscopy but by medical treatment, physiotherapy and personal exercises as stretching and strengthening muscles of the leg.

Even sometimes, the patella pain is the only pain and the meniscus lesion on the MRI is not painful. It is the clinical examination which allows making a good diagnosis to avoid surgery.

Docteur J.E. Perraudin ; last updated 1 sept 2012