The Menisci

Classification of Meniscal Lesions

Treatment Options

Surgical Indications



Each knee has two menisci, the so-called medial meniscus on the inner part of the knee and the lateral meniscus on the outside of the knee.

The menisci are considered to be a form of cartilage (therefore the term "torn cartilage" when a meniscus is torn). The menisci are located between the femur (thigh bone) and the tibia (shin bone). As seen in the accompanying figures, the menisci cannot completely cover the tibia, thus leaving an area of direct contact between the cartilage of the femur and that of the tibia. The menisci contribute to the stability of the knee (minimizing abnormal movements) and also act as a shock absorber. A tear of the meniscus may not compromise the stability of the knee if the ligaments are intact. However, a large tear can predispose to arthritis, especially if a large portion of the meniscus is surgically removed.


The lateral meniscus is located between the femur (on top in the picture) and the tibia (below in the picture). Both bones are covered with cartilage which appears white or beige in the picture. The rope-like structure seen going from top left to bottom right behind the meniscus, is the tendon of the popliteus muscle.  


Arthroscopic view of the lateral meniscus

Classification of Meniscal Lesions


Meniscal tears are divided into traumatic and non-traumatic tears : Traumatic tears can occur in knees that are essentially stable or unstable. Non-traumatic (atraumatic) lesions are divided into degenerative ("wear and tear") and tears seen in conjunction with arthritis.


Meniscal tears associated with trauma:

Traumatic tears in stable knees

The trauma here is usually indirect, meaning that there has been no specific blow to the knee. Rather, the most common mechanism of injury here is a sudden straightening and twisting of the knee as might happen when one quickly gets up from a seated position on the floor. When a sudden motion, such as the one described, is immediately followed by a locking of the knee with complete inability to straighten the knee, one can nearly be sure that a so-called "bucket handle tear" has just taken place. Such a tear also occurs as a result of athletic injuries. In the athletic setting, the doctor also looks for the possibility of a significant ligamentous injury (anterior cruciate ligament).


In this traumatic setting the most common types of meniscal tears are the bucket handle tear, the flap tear and the radial tear (and any combination of these).






Traumatic lesions in the setting of an unstable knee

Here we are talking about a direct blow to the knee, and the torn meniscus will be usually associated with a tear of the anterior cruciate ligament and possibly the medial collateral ligament. Rarely, one will find a tear of the posterior cruciate ligament or of the fibular collateral ligament. In order to make the diagnosis of a torn cruciate ligament, one must of course first think of it then confirm it by physical examination (the classic test for this is the Lachman maneuver, whereby the lower leg is pulled forward on a knee which is slightly flexed, 20-30 degrees). Plain x-rays and MRI can help confirm the diagnosis.



Atraumatic meniscal tears


Ménisques By definition, these are tears that are not the result of any single traumatic event. A meniscus can indeed tear over time and one must think of this diagnosis in the patient presenting with the gradual onset of pain (especially on the inner part of the knee). Pain in this setting tends to be cyclically with periods of waxing and waning. It is not always easy to make a specific diagnosis of a torn meniscus in this setting and one commonly may need to resort to some form of imaging (an arthrogram, or more commonly, an MRI).


Meniscal tears can sometimes be found in conjunction with arthritis (wearing out of the articular cartilage which lines the end of the femur and the tibia). The arthritis in itself can be a source of pain and removal of the torn cartilage may not improve the patient’s symptoms in this particular setting. Certainly, plain x-rays (taken in the "Schuss" position), as well as direct visualization of the knee during an arthroscopic procedure will help detect these arthritic conditions.




Treatment Options

Benign neglect. In certain conditions it is possible to leave the meniscus alone. For example, if the tear is small and the surgeon does not feel that it is a significant source of pain, it may be left alone.  

Repair. In rare cases, the cartilage can be stitched back together. The knee must be stable for this repair to have a chance of working.


"Meniscectomy." This involves the removal of the portion of meniscus which is torn.


Surgical Indications : When should the surgeon operate on a torn meniscus


There is no medical need for surgery in the setting of a torn meniscus. Indeed the only reason for recommending surgery is for pain relief. It is up to the patient to decide whether he or she is troubled enough by the torn meniscus to warrant a surgical procedure. It is not for the surgeon to determine whether a patient needs surgery. The surgeon must, however, give the patient all the information that he or she needs to make an informed decision. There is no harm in leaving a torn meniscus in place. A delay in surgery will not make the surgery more difficult nor will it be harmful to the patient in any way. The only downside to waiting is naturally the persistence of pain and possible disability as the patient waits for surgery. Surgery should not be carried out if the pain is minimal and without effect on activities of daily living. In such mild cases, a non-operative regimen is usually successful.

On the other hand, if symptoms are significant, it is a shame not to take advantage of a relatively simple procedure which can essentially eliminate the pain and disability.

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