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Torn Meniscus (Cartilage)

Each knee joint has two crescent-shaped cartilage menisci. These lie on the medial (inside) and lateral (outside) of the upper surface of the tibia (shin) bone. They are essential components of the knee, acting as shock absorbers as well as allowing for the proper interaction and weight distribution between the tibia and the femur (thigh bone). As a result, injury to either meniscus can lead to critical impairment of the knee itself.

The medial meniscus is more prone to injury than the lateral meniscus as it is connected to the medial collateral ligament and the joint capsule and so is less mobile. Hence, any forces impacting from the outer surface of the knee, such as a rugby tackle, can severely damage the medial meniscus. In addition, medial meniscal injuries are often also associated with injuries to the anterior cruciate ligament. Other mechanisms of injury may be twisting the knee or degenerative changes that are associated with age. Any of these circumstances may lead to tearing of the medial meniscus, which in serious cases may require surgical intervention.

A meniscus tear can present in various ways. Sometimes a “popping” sensation is experienced by the person during a traumatic event. There is usually significant pain along the joint line on the side of the tear (medial or lateral). Sometimes people can continue to walk on the knee, while other large tears may cause too much pain to allow for weight bearing. Sometimes the tear pattern can cause a portion of the meniscus to become entrapped between the joint surfaces or within the notch of the knee. In these cases, the knee is often locked and the athlete cannot flex or extend the knee. The classic signs to look for with a meniscus tear include:

• Pain, often along the joint line of the knee

• Swelling (“effusion” in the joint) often develops due to inflammation and/or bleeding from the injury

• Inability to fully extend or flex the knee without discomfort

• Locking or catching of the knee

• Weakness of the leg, particularly the quadriceps muscle. This may be evident when trying to perform a straight leg raise or walk up and down stairs.

In addition to examining for the above signs and symptoms, a physician may check the athlete’s ability to squat on the knee without discomfort. They doctor may also perform a McMurray’ Test in which the knee is bent, straightened, and rotated in an attempt to entrap the meniscus tear within the joint. If you have a meniscus tear, this movement may reproduce clicking and pain.

What imaging studies help to confirm the presence of a meniscus tear?

Plain x-rays (radiographs) of the knee can be useful to evaluate for the presence of associated injuries such as tibial plateau fractures or ligament avulsions. They will not, however, confirm or rule out the presence of a meniscus tear.
Magnetic resonance imaging (MRI) of the knee has become the gold standard of imaging studies for a meniscus tear. These high-resolution pictures from multiple perspectives allow for a greater than 95% sensitivity in detecting a meniscus tear. Furthermore, they provide valuable information regarding the tear pattern and configuration to help preoperative planning and assessment of the repairability of the tear.

MRI of the knee not only helps to define the tear, but allows for evaluation of the other important anatomical structures of the knee. The status of the collateral and cruciate ligaments, as well as the cartilage surfaces of the joint can be carefully evaluated to help design the best treatment plan.

In some situations, your surgeon may offer a meniscus repair as a possible surgery for damaged or torn cartilage. Years ago, if a patient had torn cartilage, and surgery was necessary, the entire meniscus was removed. These patients actually did quite well after the surgery. The problem was that over time, the cartilage on the ends of the bone was worn away more quickly. This is thought to be due to the loss of the cushioning effect and the diminished stability of the joint that is seen after a meniscus is removed.

When arthroscopic surgery became more popular, more surgeons performed partial menisectomies. A partial meniscectomy is performed to remove only the torn segment of the meniscus. This works very well over the short and long term if the meniscus tear is relatively small. But for some large meniscus tears, a sufficient portion of the meniscus is removed such that problems can again creep up down the road.

Depending on the location of the tear, a repair may be possible. In the outer third of the meniscus, an adequate blood supply exists and a repair will likely heal.[1] Usually younger patients are more resilient and respond well to this treatment, while older, more sedentary patients do not have a favorable outcome after a repair.

The meniscus has fewer vessels and blood flow towards the unattached, thin interior edge. In the majority of cases, the tear is far away from the meniscus' blood supply, and a repair is unlikely to heal. In these cases arthroscopic surgery allows for a partial meniscectomy, removing the torn tissue and allowing the knee to function with some of the meniscus missing. In situations where the meniscus is damaged beyond repair or partial removal, a total menisectomy is performed. This option is avoided at all costs as total meniscectomy leads to an increased risk of osteoarthritis (with loss of cartilage) and eventual total knee replacement. In some cases, a meniscus replacement is done to prevent this.

Recently, transplants of full meniscus are accomplished successfully regularly, although it is still somewhat of a rare procedure and many questions surrounding its use remain.

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