Medial Meniscus Tear

Medial meniscus tears are common knee injuries and occur in about 61 per 100,000 people. Surgeries pertaining to meniscus are carried out on approximately 85,000 patients each year. Then how is it that we don't hear this term being used so often? The reason is because medial meniscus tear is most commonly known as 'torn cartilage'. Athletes are often seen to suffer from this kind of an injury, as they often encounter traumatic forces while playing or training for the sport.

Anatomy of Meniscus

The knee joint - the largest joint in the body is a complex joint and consists of three bones: Femur bone (thigh bone), Tibia (bone of the lower leg) and the Patella (knee cap). Each of these bones are covered by a thin layer of articular cartilage, which is hard but smooth in nature and reduces friction between the bones. Besides the bones, four ligaments are also present: Anterior cruciate ligament (ACL), Posterior cruciate ligament (PCL), Medial collateral ligament (MCL) and the Lateral collateral ligament (LCL) which stabilize the knee, thereby providing strength to the knee joint.

There exists two wedge-shaped, thick, rubbery menisci (plural of meniscus) situated in each knee, that are located on the medial (inner side) and lateral (outer) sides of the knee joint. Based on their location they are termed as medial meniscus (C- shaped) and lateral meniscus (O-shaped). Medial meniscus is slightly larger and is only half as mobile as the lateral meniscus. The peripheral, convex border of the meniscus is thicker as compared to the inner/central portion.

The menisci, sandwiched between the femur and the tibia are held in place by the coronary ligaments. The wedged shape of the meniscus enables it to keep the rounded condyles of the femur from sliding off the almost flat tibial surface. The meniscus is popularly known as the 'cartilage' of the knee, however, it is composed of dense fibro-cartilage, making it flexible and not as hard as articular cartilage.

Small blood vessels provide blood supply to the meniscus. However, not the entire portion of the meniscus receives blood supply. The central portion of the meniscus is avascular (no blood supply).The menisci are divided into various zones based on the blood supply available to them, namely, the red zone (peripheral meniscus) which receives vascular (blood) supply, the red-white zone with blood supply only in its outer region and the white zone (central meniscus) which lacks blood supply.

Medial Meniscus

The C-shaped medial meniscus is asymmetric, with the anterior horn wider than the posterior horn. It is approximately 3.5 cm in length and is attached to the medial collateral ligament (MCL). The peripheral part is attached to the joint capsule and the middle portion is firmly attached to fibers of the medial collateral ligament. Thus, it is common to find medial meniscus tear occurring with simultaneous tears in the anterior cruciate ligament and the medial collateral ligament due to their interconnections. This triple rupture phenomenon is called as 'unhappy triad'.

Function of the Meniscus

Shock Absorber: The menisci cushion the forces that are directed upward or downward through the knee. They spread out the forces being transferred from the thigh to the lower leg and diminish the load borne by the spine, pelvis, hip, ankle and foot joints.

Protects Articular Cartilage: The menisci prevent the wear and tear of the articular cartilage by spreading out the forces (during walking, running) applied on the knee joint surfaces. In the absence of the meniscus, a large amount of force would have been concentrated on the small area of the articular cartilage leading to damage and degeneration (osteoarthritis).

Nutrition: The repeated loading and unloading action of the joint helps in lubrication and nourishment of the cartilage. The menisci also assist in nutrition of the knee joint.

Knee Stability: The wedge shape of the meniscus helps it to deepen the almost flat tibial surface into a shallow socket, thereby allowing the femur to easily slide over the tibia.

Even distribution of body weight: The meniscus evenly distributes the forces applied on the knee joint, by distributing the forces across a large area and minimizing focal contact pressure.

Load bearing: The meniscus bears around 40% of the total weight applied on the knees and reduces the load on the articular cartilage.

Medial Meniscus Tear

Twisting or application of abnormal pressure on the medial meniscus causes the meniscus to get jammed between the bones, thereby resulting into tearing or splitting of itself and is called as medial meniscus tear. Medial meniscus gets 10 times more frequently injured, as compared to the lateral meniscus. This is because the medial meniscus is more firmly attached to the tibial surface and knee joint capsule.

Traumatic or stressful activities encountered during sports (football, rugby) involving sudden twisting of the knee when the foot is planted on the ground (weight-bearing position) can result in medial meniscus tear. Most commonly, medial meniscus tears are seen to occur in situations when the knee is in the bent position and twisting occurs on the bent knee. Severe pain and swelling within 24 hours occur subsequently.

Loss of resiliency of the meniscus can also lead to medial meniscus tears. This is seen in older people whose meniscus happen to degenerate on aging and is termed as 'degenerative tear'. Sometimes, when the tear is mild, it goes unnoticed. However, years later it may resurface by a movement as mere as walking, tripping or squatting. Injury to the medial meniscus can happen to people of all ages. However, the healing process in every age group is different. In younger people, the meniscus is tough and rubbery, whereas in older age groups the meniscus becomes weak with age. Young people's menisci respond to treatment more readily as compared to older people, who have unfavorable outcomes even after surgery.

The size and variety of each medial meniscus tear can vary widely, thus the severity of the tear depends on the size and type of tear. The different types of medial meniscus tears are bucket handle tears (longitudinal tear with the shape of a bucket handle), radial tears, horizontal tears, parrot beak tears and complex tears. The medial meniscus may be torn in half, cut off in the shape of a C along the circumference or can also hang loosely from the knee joint by a thread. The zone of meniscus where injury occurs also matters. If the injury has occurred at the peripheral region, then healing will take place faster, due to the blood supply. However, for injuries occurring at the white zone, the lack of blood supply hinders the healing process.

Symptoms of Medial Meniscus Tear:

• Pain in the knee area
• Swelling of the knee joint
• Increased temperature of the knee, inflammation
• Stiffness and tightening of the knee
• Flexing is possible, however leg extension becomes painful.
• Difficulty bending, squatting
• Walking becomes difficult
• Instability and performing normal activities become difficult.
• On pressing the knee joint line, tenderness is produced.
• Sensation that the knee is giving away
• Knee clicking
• Knee catching
• Knee locking

Knee locking is a condition in which one cannot extend the knee. This happens when a loose piece of the meniscus gets stuck in the knee joint causing inability (temporary) to extend the leg completely. Only larger and more severe tears result into knee locking and giving way signs.

Treatment

Early Injury Treatment: The 'RICE' treatment is followed to control the swelling and pain, for the first 72 hours after the injury. RICE stands for Rest, Ice, Compression and Elevation. The wounded person must restrain from any kind of aggravating activities. An ice pack is placed for the next 72 hours, which must be applied 15-20 at a time. The ice however is not allowed to come in direct contact with the skin and is placed in a wet towel or cloth. Elastic bandage serves as the medium for the obtaining compression. The fourth step is to elevate the injured portion above the heart level, so as to allow the swelling to go back to the heart via the bloodstream.

Scan and X-rays: From the symptoms, a doctor can clinically diagnose meniscus injury, but the will still need to get diagnostic imaging done in order to determine the extent of the injury. The X-Rays usually do not reveal medial meniscus tears. Magnetic Resonance Imaging (MRI) is used for meniscus tear diagnosis. The meniscus appears black on the MRI and any kind of tear or rupture appears in the form of white lines. MRI's are not always reliable, as sometimes they do not reveal meniscus tears. Arthroscopy is a reliable way to determine the tear, however, it's an expensive method.

Conservative/ Traditional Method: This traditional form of treatment involves physical therapy in order to treat the injury. The patient undergoing this treatment has to refrain from performing routine activities; taking complete rest and allowing the knee to heal. Physical exercises carried out later on strengthen the muscles around the knee.

Surgery: Cases wherein physical therapy fails to bring about healing and where knee locking has occurred, surgery is carried out. Depending on the severity of the injury, the surgeon may either repair, remove or replace the meniscus.

A severe medial meniscus tear can bring about drastic changes in a person's life. Performing daily routine activities, and work and play become difficult. Thus proper functioning of the meniscus is crucial for the health of not only our knees, but also our lives.