The meniscus is easily injured by the force of rotating the knee while bearing weight. A partial or total tear may occur when a person quickly twists or rotates the upper leg while the foot stays still (for example, when dribbling a basketball around an opponent or turning to hit a tennis ball). If the tear is tiny, the meniscus stays connected to the front and back of the knee; if the tear is large, the meniscus may be left hanging by a thread of cartilage. The seriousness of a tear depends on its location and extent.
Generally, when people injure a meniscus, they feel some pain, particularly when the knee is straightened. If the pain is mild, the person may continue moving. Severe pain may occur if a fragment of the meniscus catches between the femur and the tibia. Swelling may occur soon after injury if blood vessels are disrupted, or swelling may occur several hours later if the joint fills with fluid produced by the joint lining (synovium) as a result of inflammation. If the synovium is injured, it may become inflamed and produce fluid to protect itself. This makes the knee swell. Sometimes, an injury that occurred in the past but was not treated becomes painful months or years later, particularly if the knee is injured a second time. After any injury, the knee may click, lock, or feel weak. Although symptoms of meniscal injury may disappear on their own, they frequently persist or return and require treatment.
In addition to listening to the patient's description of the onset of pain and swelling, the doctor may perform a physical examination and take x rays of the knee. The examination may include a test in which the doctor bends the leg, then rotates the leg outward and inward while extending it. Pain or an audible click suggests a meniscal tear. An MRI may be recommended to confirm the diagnosis. Occasionally, the doctor may use arthroscopy to help diagnose and treat a meniscal tear.
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If the tear is minor and the pain and other symptoms go away, the doctor may recommend a muscle-strengthening program. Exercises for meniscal problems are best started with guidance from a doctor and physical therapist or exercise therapist. The therapist will make sure that the patient does the exercises properly and without risking new or repeat injury. The following exercises after injury to the meniscus are designed to build up the quadriceps and hamstring muscles and increase flexibility and strength.
- Warming up the joint by riding a stationary bicycle, then straightening and raising the leg (but not straightening it too much).
- Extending the leg while sitting (a weight may be worn on the ankle for this exercise).
- Raising the leg while lying on the stomach.
- Exercising in a pool (walking as fast as possible in chest-deep water, performing small flutter kicks while holding onto the side of the pool, and raising each leg to 90 degrees in chest-deep water while pressing the back against the side of the pool).
If the tear is more extensive, the doctor may perform arthroscopic or open surgery to see the extent of injury and to repair the tear. The doctor can sew the meniscus back in place if the patient is relatively young, if the injury is in an area with a good blood supply, and if the ligaments are intact. Most young athletes are able to return to active sports after meniscus repair.
If the patient is elderly or the tear is in an area with a poor blood supply, the doctor may cut off a small portion of the meniscus to even the surface. In some cases, the doctor removes the entire meniscus. However, osteoarthritis is more likely to develop in the knee if the meniscus is removed. Medical researchers are investigating a procedure called an allograft, in which the surgeon replaces the meniscus with one from a cadaver. A grafted meniscus is fragile and will shrink and tear easily. Researchers have also attempted to replace a meniscus with an artificial one, but this procedure is even less successful than an allograft.
Recovery after surgical repair takes several weeks, and postoperative activity is slightly more restricted than when the meniscus is removed. Nevertheless, putting weight on the joint actually fosters recovery. Regardless of the form of surgery, rehabilitation usually includes walking, bending the legs, and doing exercises that stretch and build up leg muscles. The best results of treatment for meniscal injury are obtained in people who do not show articular cartilage changes and who have an intact ACL.
Source: National Institute of Arthritis and Musculoskeletal and Skin Diseases
Reviewed: May 2001
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