What is a Torn Meniscus?
What is a meniscus?
There are two menisci in your knee; each rests between the thigh bone (femur) and shin bone (tibia). The menisci are made of tough cartilage and conform to the surfaces of the bones upon which they rest. One meniscus is on the inside of your knee; this is the medial meniscus. The other meniscus rests on the outside of your knee, the lateral meniscus.
What does the meniscus do?
These meniscus functions to distribute your body weight across the knee joint. Without the meniscus present, the weight of your body would be unevenly applied to the bones in your legs (the femur and tibia). This uneven weight distribution would cause excessive forces in specific areas of bone leading to early arthritis of knee joint. Therefore, the function of the meniscus is critical to the health of your knee.
How does the meniscus work?
The knee joint is very important in allowing people to go about performing almost any activity. The joint is made up of three bones: the femur (thigh bone), the tibia (shin bone), and the patella (knee cap). The surfaces of these bones within the joint are covered with a layer of cartilage. This important surface allows the bones to smoothly glide against each other without causing damage to the bone. The meniscus sits between the cartilage surfaces of the bone to distribute weight and to improve the stability of the joint.
What is knee cartilage? Is it the meniscus or the ends of the bone?
Both the covering of the bone within the joint and the meniscus are made of cartilage–this makes the issue a little confusing. People often say ‘cartilage’ to mean the meniscus (the wedges of cartilage between the bone) or to mean the joint surface (so-called articular cartilage which caps the ends of the bone).
When people talk about a cartilage tear, they a talking about a meniscus tear. When people talk about arthritis and wear of cartilage, they are talking most often about the articular cartilage on the ends of the bone. Hopefully that clears up some of the confusion.
The meniscus is C-shaped and has a wedged profile. The wedged profile maintains the stability of the joint by keeping the rounded femur surface from sliding off the flat tibial surface. The meniscus is nourished by small blood vessels, but the meniscus also has a large area in the center of that has no direct blood supply (avascular). This presents a problem when there is an injury to the meniscus as the avascular areas tend not to heal. Without the essential nutrients supplied by blood vessels, healing cannot take place.
What happens with a meniscus tear (torn cartilage)?
The two most common causes of a meniscus tear are due to traumatic injury (often seen in athletes) and degenerative processes (seen in older patients who have more brittle cartilage). The most common mechanism of a traumatic meniscus tear occurs when the knee joint is bent and the knee is then twisted.
It is not uncommon for the meniscus tear to occur along with injuries to the anterior cruciate ligament (ACL) and the medial collateral ligament (MCL)-these three problems occurring together are known as the “unhappy triad,” which is seen in sports such as football when the player is hit on the outside of the knee.
