The knee is the largest joint in the human body and proper function and health of the knees is required to perform most everyday activities. The knee is made up of the lower end of the femur (thighbone), the patella (kneecap), and the upper end of the tibia (shinbone). Articular cartilage, which is a smooth substance that protects the bones and allows them to move freely, covers the ends of the three bones and acts as the main "shock-absorber". Between the femur and the tibia are two C-shaped cushioning wedges known as the menisci that act as the secondary "shock absorbers". Large ligaments (tough bands of tissues) help hold the femur and the tibia together in order to stabilize the joint by preventing excessive movement. The lining joint is covered by the synovial membrane, which is a thin lining that releases fluid that lubricates the cartilage, reducing the friction within the knee joint and providing nutrition to the cartilage. All of these components work together to facilitate proper function of the knee.
The menisci are tough and rubbery pieces of cartilage that fill the gap between the tibia and the femur and help cushion the joint and keep it stable. The outer edges of the menisci are fairly thick while the inner surfaces are thin to conform to the wedges of bone surrounding them. The medial meniscus is more commonly injured than the lateral meniscus as it is firmly attached to the medial collateral ligament and joint capsule. The medial meniscus and lateral meniscus were once thought to be of little use and were often removed when torn. However, more recently, their importance in joint stability, lubrication, and force transmission have become evident.
Meniscal tears are among the most common knee injuries, particularly among athletes who play contact sports. Meniscal tears can often occur during sports where an athlete may squat and twist the knee, causing a tear, or when a player is contacted by another player. Tears that occur as a result of sports related activities are generally diagnosed soon after the injury and are called acute tears. However, anyone at any age can tear a meniscus. When they occur in adults they are most commonly chronic, degenerative tears caused by repetitive use.
Individuals who experience a meniscal injury generally have the following signs and symptoms:
- Hearing or feeling a popping sensation in the knee
- Swelling or stiffness in the knee joint
- Pain that increasing with twisting or rotating the knee
- Inability or difficulty in fully straightening the knee
- Impaired range of motion - a sensation of catching or locking of the knee
Without treatment, a piece of meniscus may come loose and move into the joint which can cause the knee to slip, pop, or lock. Therefore, it is highly advised to visit a physician if an individual experiences the symptoms mentioned above.
A meniscal injury is typically diagnosed with a combination of patient history, physical examination as well as imaging studies. The physician will examine the knee to assess the range of motion, stability, swelling, tenderness, and overall strength compared to the uninjured knee. The physician may conduct the McMurry test where the knee is bent and then rotated repeated to see if the tension on the meniscus causes pain. Since other knee problems tend to cause similar problems, the physician may order X-rays to evaluate damage to the bones or osteoarthritis. An MRI scan may be needed to determine the extent of damage as well as the location and nature of the tear.
The menisci may tear in different ways which can be determined by the nature and location of the tear. A tear may be located in the anterior horn, body, or posterior horn and the meniscus is further broken down into the outer, middle, and inner thirds. The third in which the tear is located will determine the ability of the tear to heal, since blood supply in that area is critical to the healing process. Tears in the outer third have the best chance of healing with treatment as the blood supply is significantly richer here than in the middle and inner thirds.
Treatment for a meniscal injury or tear will vary depending on the individual based on the severity of the damage, age, the level of activity they wish to resume, and the location / type of tear. If the tear is small and on the outer edge of the meniscus, operative treatment might not be required provided the symptoms reduce with time and the knee is stable.
Non-Operative Treatment - The immediate treatment for a meniscal injury is the self-care RICE approach:
- Rest - Walking will be painful, so it's best to avoid putting pressure on the injured knee and limiting activity while inflammation persists.
- Ice - Ice should be applied for the first 48 to 72 hours or until the swelling subsides for 10 to 20 minutes no more than once per hour. Use of a barrier, such as a towel, is strongly advised to protect your skin. Heat should be avoided while inflammation is developing; once the swelling goes down, heat can help soothe the pain.
- Compression - Using a compressing wrap can help significantly decrease swelling. Ensure that the wrap is snug; however, if there is numbness, tingling, or swelling above or below the wrap, it's probably on too tight and needs to be loosed.
- Elevation - Raising the knee above the heart level for a few hours a day can aide tremendously in decreasing swelling.
Medication - Over-the-counter anti-inflammatory medication such as ibuprofen and naproxen usually help reduce pain and swelling.
Operative Treatment - Once the initial swelling goes down with the help of the RICE approach, the patient and the physician will need to decide on the proper treatment plans. Considerations include, displaced tear is causing the joint to lock, and especially if the anterior cruciate ligament (ACL) is also torn or injured. The procedure chosen to treat a meniscal tear is usually dependent on the location and type of meniscal tear.
Small incisions are made around the joint where surgical instruments and the arthroscope (a small camera) will be inserted and the image will be sent to a video monitor allowing the physician to see inside the joint. Using the surgical instruments, the torn ACL is completely removed. The next step is preparation and the insertion of the graft:
- Partial Meniscectomy - This surgery is used for tears with low potential to heal such as the part located in the inner two-thirds of the meniscus where there is no blood supply. The aim of this procedure is to stabilize the rim of the meniscus by removing as little of the meniscus as possible. The surgical instruments are inserted into the knee through an incision around the joint and used to trim the torn piece of meniscus.
- Meniscal Repair - This surgery is used for clean tears located in the outer one-third of the meniscus where there is good blood supply. The surgical instruments are inserted into the knee through an incision around the joint and used to repair the damaged meniscus with the use of various devices as deemed appropriate by the physician.
Regardless of the treatment approach taken, patients go through a rehabilitation program which includes physical therapy exercises that are crucial to strengthen your leg muscles and regain knee strength and motion. Each patient is unique, so the therapy program will vary based on his/her level of pain, extent of injury, and desired level of activity. For patients who have undergone partial meniscetomy, recovery can take upwards of six weeks. However, if an individual has undergone a meniscal repair, recovery can take three to six months.
CALL 911 IMMEDIATELY IF YOU ARE HAVING A MEDICAL EMERGENCY!
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