A torn meniscus: what it is and what it means
Knee problems send almost 20 million people to a doctor’s office each year. Injuries to the knees are common to all sports and cumulative wear and tear on the knee sends large numbers of older people to doctors’ offices as well.
“The knee is vulnerable to injury because it is a hinged joint,” says Dr. Stuart Styles, knee treatment specialist with Somers Orthopaedic Surgery & Sports Medicine Group. “That means it moves in two directions as it bends and straightens, but in a single plane. When forces are applied to the knee from outside that plane — as in, say, a football tackle — injury is likely to one or more of the components of the knee: the bones, cartilage, muscles, ligaments, or tendons.”
Meniscus tears are among the most common knee injuries, occurring in people of all ages, both athletes and non-athletes. According to Dr. Styles, “The first question many patients ask about a torn meniscus is ‘can it be fixed?’ Yes, most of the time a torn meniscus can be successfully treated, but not all meniscus tears need to be fixed.”
Tips for understanding torn meniscus treatment
How a meniscus tear is treated depends on the type of tear, its size and where it is located. The outer rim of the meniscus has a rich blood supply and a small tear in that area may heal on its own, with rest; a larger tear in that area can be repaired surgically and tends to heal well. A tear toward the center of the meniscus, where the blood supply is poor, will not heal as well and the area of torn cartilage may be trimmed away rather than repaired.
“Years ago, a torn meniscus was simply removed entirely,” says Dr. Styles. “But we now have a much better understanding of the importance of the meniscus to maintaining the full function of the knee over the long term and we repair whenever possible. If repair isn’t feasible, we remove as little as possible of the cartilage.” Removing small bits of torn cartilage has little or no adverse effect on the knee’s function and is preferable to leaving the tear in place, which is likely to contribute to the development of arthritis over the long term.
Increasingly, arthroscopic surgery is used on meniscus injuries, which eliminates the need to open the knee. Through a small incision, the surgeon inserts a thin tube that contains a camera and a light that illuminate and magnify the inside of the joint, projecting the images on a screen. Surgical instruments are also manipulated through small incisions, reducing discomfort for the patient and hastening recovery.
What is a meniscus?
Three bones form the knee joint, which acts as a hinge to provide motion where the thigh meets the lower leg. The thigh bone (femur) meets the large bone of the lower leg (tibia) at the knee, protected in the front by the kneecap (patella). The menisci are two crescent-shaped pieces of cartilage that act as shock absorbers, spreading compression forces from the femur over a wider area of the flat upper surface of the tibia. In addition to providing cushioning, the menisci help stabilize the bones and play a role in keeping the knee lubricated with synovial fluid, which is released by a thin, smooth tissue liner called the synovial membrane. In a healthy knee, all these parts work together smoothly and friction is reduced to nearly zero.
The two menisci in each knee are the medial and the lateral. The medial meniscus is located on the inside of the knee and is the one most often injured because it is firmly attached to the medial collateral ligament, one of the major ligaments of the knee. The lateral meniscus is on the outside of the knee and has more mobility because it is not attached to the lateral collateral ligament. As we walk, forces on the knee shift from one meniscus to the other and may equal two to four times body weight. When we run and jump, these forces are many times higher.
How does the meniscus tear?
Acute injuries to the meniscus happen in an instant, often on the playing field, as a result of awkward or forceful bending or twisting when the knee is in a weight-bearing position. Acute tears often accompany injury to other parts of the knee, like the ligaments, and imaging tests might be needed to pinpoint the damaged components. Degenerative injuries occur most commonly in older people. With age, the meniscus weakens and loses elasticity and is more prone to tearing, even as a result of a seemingly insignificant motion. Most people over the age of 65 have some degenerative damage to the meniscus, sometimes a small tear that causes little or no discomfort.
Some people feel a pop when a meniscus tears. Most have symptoms such as pain, swelling, stiffness, a clicking noise, locking of the knee or a feeling of the knee giving way.
Life after meniscus treatment
“We have been very successful treating meniscus injuries,” Dr. Styles concludes. “And while there’s no magic formula for keeping knees healthy, there are steps everyone can take to minimize the risk of injury. The most important is to maintain the strength and flexibility of the muscles that stabilize the knee — the quadriceps and hamstring. Another is to wear shoes that are appropriate for each activity and that reduce the risk of bending and twisting that can damage the knees. Take care of your knees and they’ll take you wherever you want to go.”
Stuart T. Styles, M.D., F.A.A.O.S. is a board certified orthopaedic surgeon with Somers Orthpaedic Surgery & Sports Medicine and a clinical assistant professor in orthopaedic surgery at NYU School of Medicine/Hospital for Joint Diseases Orthopaedic Institute.