This article is from the WebMD Feature Archive

April 6, 2000 (Atlanta) -- Knee cartilage tears are among the most common injuries in football, basketball, hockey, soccer, and just fooling around in the backyard. While seldom does a meniscal tear cause a season-ending injury -- recently the 7-foot-7-inch center of the New Jersey Nets missed just six weeks after his was repaired -- if not diagnosed and treated properly, it can degenerate and cause problems throughout life.

In a report in the March edition of The Physician and Sportsmedicine, Joseph Bernstein, MD, MS, describes the typical diagnosis and treatment of meniscal cartilage tears. Bernstein is director of sports medicine at the University of Pennsylvania in Philadelphia.

David R. Diduch, MD, of the department of orthopaedic surgery at the University of Virginia, describes the meniscus as a semicircular, crescent-shaped structure in the knee between the femur (thigh bone) and the tibia (shin bone). There is one on either side of the knee: the medial meniscus on the inner side and the lateral meniscus on the outer side, attached to the tibia by ligaments.

The cartilage ring is thickest at the periphery and tapers toward the center, creating a cup-like structure for the rounded end of the femur. Besides helping to stabilize the knee joint, the meniscus cartilage acts as a sort of gasket between the femur and the tibia. In essence, it spreads out the weight being transferred from the femur above to the tibia below.

In younger people, the meniscus is a fairly tough and rubbery structure. In people under age 30, tears usually occur as a result of a fairly forceful twisting injury. In the younger age group, meniscal tears are more likely to be caused by a sport activity. But the meniscus grows weaker with age; the tissue that makes up the meniscus degenerates and is much easier to tear. Meniscal tears in older people can occur as a result of a fairly minor injury, even from the up and down motion of squatting.

Can meniscal tears be prevented or the risk minimized for young or old? "I don't think so," Bernstein tells WebMD. "At least with current know-how. I actually have an idea that there can be things done to rejuvenate the decaying meniscus, but that is science fiction for now."

Bernstein says that athletes can sometimes continue to play with a tear, but their performance suffers. Eventually, lack of treatment can cause damage and degeneration of the joint. "Even if the patients are able to ignore symptoms, they should be dissuaded from doing so, especially if the tear is repairable," writes Bernstein.

Individuals who have a meniscal tear usually complain of pain and swelling as their primary symptoms. The sufferer may also experience joint locking, or the inability to completely straighten the joint. This is due to a piece of the torn meniscus physically impeding the joint mechanism of the knee.

In diagnosing a meniscal injury, the physician should first rule out other injuries, especially those associated with twisting. If he believes it's a tear, he should determine if it is repairable. "Assume that all patients younger than age 35 have potentially repairable tears," says Bernstein.

If there's swelling, sometimes the knee is drained to help identify the underlying cause. Bernstein says that blood in the knee may mean it's not a cartilage tear. Since the meniscus doesn't have veins or arteries, the blood must come from somewhere else. "There is rarely swelling of the variety seen with, say, ankle sprains," says Bernstein. "Since the inside of the knee ordinarily gets scant blood supply ... there's no rapid inflammation. However, blood vessels may burst, causing bleeding within the knee, but that is not [really] swelling ... but rather something on which we stick the fancy name 'hemarthrosis.'" Joint fluid (effusion) may build up over days if there are mechanical irritants in the knee, such as torn cartilage.

Using MRI for diagnosis is a hotly debated topic, says Bernstein. The advantages are that it involves minimal risk to the patient and that it yields a fairly accurate picture of soft tissues of the knee. "Accuracy is approximately 90%," he says. Also, MRI may reveal abnormalities that were not suspected on the clinical exam and thus may influence treatment.

There are generally three treatment options for meniscal tears. Nonsurgical treatment includes the use of anti-inflammatory medications as well as physical therapy to prevent weakness and stiffness of the quadriceps, the large muscles in the front of the thigh. One drawback to this approach is that a potentially repairable tear may become irreparable. Small tears are especially good candidates for nonoperative therapy.

Partial tears are repaired arthroscopically. According to the American Academy of Orthopaedic Surgeons, in an arthroscopic examination, an orthopaedic surgeon makes a small incision in the patient's skin and then inserts pencil-sized instruments, called arthroscopes, that contain a small lens and lighting system to magnify and illuminate the structures inside the joint. Via a miniature camera, the surgeon is able to see the interior of the joint through this very small incision rather than the large incision needed for traditional surgery. The surgeon can determine the amount or type of injury and then repair or correct the problem, if it is necessary.

This minimally invasive approach lessens the disruption of normal tissue and allows for rapid rehabilitation. Arthroscopy leads to less swelling, faster achievement of full movement, and a quicker return to activities. The main drawback of this option is that meniscal tissue is lost, creating some risk for degeneration. Bernstein says this option should only be considered by patients who are sufficiently bothered by their tear, and for whom meniscal repair is not possible.

In meniscal surgery, the torn edges of the meniscus are stitched together to preserve the form and function of the cartilage. According to Bernstein, research shows that approximately 90% of such peripheral meniscal tears do heal. There's also evidence that repaired menisci can prevent joint degeneration.

But not all patients are candidates for meniscal repair, especially when the tissue is too damaged to save. Also, since the meniscus itself doesn't have a blood supply, only tears at the periphery of the meniscus, adjacent to the blood supply, are likely to heal.

Research is being conducted on transplanting meniscal tissue from other sources and trying to grow this tissue in the laboratory for transplantation into humans.

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