Meniscal Injuries

How often have you heard friends or athletes complain that they had "torn cartilage" in their knees? They are probably not talking about the cartilage that covers the end of the bone in the knee. Instead they may have another type of cartilaginous injury: a meniscal tear.

Anatomy
Each knee contains two menisci, one medial and one lateral (Fig. 1). They are fibrocartilaginous disks that act as cushions between the ends of the femur (thigh bone) and the tibia and fibula (lower leg bones). The top of the tibia is flat and the ends, or condyles, of the femur are rounded (Fig. 2). The menisci help make a more concave surface for the condyles to rest and glide on, making the knee joint more stable. The medial meniscus is attached to the ligaments on the back and medial, or inner, side of the knee. Because it is attached so securely, it does not move freely and so it is torn more often than the lateral meniscus, on the outside half of the joint. The lateral meniscus is attached only at the back of the knee and moves more freely as the knee is bent and straightened.

How injury occurs
The menisci can be torn when the knee is twisted suddenly and one or both menisci become trapped between the femur and tibia. They can also be torn when the ligaments in and around the knee are torn. As you age your menisci can lose their rubbery consistency and soften and fray. These weakened structures can be torn more easily, with just a misstep around the house.

When the meniscus tears, you will usually feel a sharp pain on the side of the knee that was injured. The initial pain and swelling will go away, but you might continue to have sharp pain in the knee when turning suddenly. The knee might catch or lock when you bend or straighten it, or you might not be able to bend or straighten the knee all the way.

To diagnose meniscal tears, the physician performs certain tests or maneuvers and asks you to describe the injury and symptoms. X-rays of the knee are usually Laken to make sure there is no joint degeneration, loose bodies, or other bone abnormalities. However, the menisci are soft tissue so tears are not visible on plain x-rays. Because meniscal tears show up on magnetic resonance imaging (MRI), the physician can use MRI to accurately confirm the tear if necessary.

Depending on the type and location of the tear and the severity of the symptoms, nonsurgical management can be tried. For meniscal injuries this includes physical therapy to maintain or increase muscle strength and range of motion, activity modification, antiinflammatory medications, support sleeves, and time. Generally, 1 to 3 months is a reasonable time expectation for significant improvement.

Surgical treatment
Patients who do not improve with the nonsurgical management often need surgery. Most tears are removed or trimmed, but about 1 0% of recent, or acute, tears can be surgically repaired. Tears that occur in the outer edge of the meniscus have a better chance of healing when repaired than those farther in the joint. The outer rim has more blood vessels to help the healing process.

Arthroscopic removal or repair can usually be done as an outpatient procedure in about an hour. The surgeon inserts instruments through two to four small portals, or 1 -cm skin incisions. The instruments allow the surgeon to see and treat the torn meniscus. To repair the torn meniscus, the surgeon might need to make a larger incision around the knee. In knees that are unstable because of ligamentous injuries (for example, anterior cruciate ligament tears), the ligaments are repaired along with the meniscus because an unstable knee can cause further meniscal tears or degenerative changes.

Recovery from surgery varies for different people and for different clinical problems. Patients who have a torn meniscus removed or trimmed can expect to use crutches or a walker for 4 to 7 days. They may have some swelling for 3 to 6 weeks and can return to their normal activities in 4 to 6 weeks, if not sooner. If the meniscus has been repaired, weight bearing may be limited with use of crutches for 4 to 6 weeks. This will allow the repaired meniscus to heal. Compared with open knee surgery, with more extensive surgical incisions, arthroscopic surgery causes limited scarring, has a quicker recovery time, and allows a quicker return to work or athletics.

The meniscus plays a key role in cushioning the knee joint and preventing premature arthritis. But if the menisci are torn, painful knee problems can occur that often need to be corrected by surgery. Modern arthroscopic surgery has improved the results of surgery for meniscal injuries and has allowed a quicker return and greater functional recovery for this bothersome condition.

William Sutton, M.D.
Wilmington, North Carolina