The anterior cruciate ligament (ACL) is a ligament in the knee. Sometimes this ligament can tear, especially during sports that involve sudden stops and changes in direction.Here’s what you need to know about how ACL injuries occur, how they are diagnosed, and what you can expect from treatment and rehabilitation
Part 1: What does a meniscus do and why should we care? Part 1 of 3
The meniscus is a C-shaped pad of fibrous cartilage in the knee. Each knee has two menisci, and these are essential for the long-term health of the knee. One of their most important functions is as shock absorbers in the knee joint.
What is a meniscus?
The menisci are tough, smooth and rubbery, crescent-shaped wedges of fibrocartilage which sit between the femur (thighbone) and tibia (shinbone) where they meet in the knee joint.
The meniscus is named after its shape – which resembles a crescent moon. In Greek, “meniskos” means “crescent”, which is a diminutive of “mene” meaning “moon”.
Incredibly, the meniscus is already present in a foetus from around the eighth week of gestation!
What is the meniscus made of?
The meniscus is made of a type of cartilage called fibrocartilage which consists predominantly of water and collagens.
Around 75% of the weight of the meniscus is made up of water. As a person ages, the meniscus loses water and becomes more rigid. That is why older people may tear their meniscus during a less dramatic event than younger people.
Various types of collagens make up around 75% of the organic matter or dry weight of the meniscus. The rest of the dry matter is made up of proteins, blood vessels and other cells.
Why are menisci so important?
The menisci are a vital part of the knee, playing a protective role by reducing wear and tear on the cartilage and bones in the knees. These are some of the important ways they function and contribute to the overall health of the knee.
- Shock absorption and load bearing: The menisci act as shock absorbers – absorbing the weight of our bodies when we walk or stand and distributing the load evenly across the joint. I like to compare the menisci to the shock absorbers on our cars – they preserve the tyres and ensure a smooth ride.
- Joint stability: The menisci keep the knee joint stable.
- Joint nutrition and lubrication: When we walk, the menisci are compressed, squeezing liquid into the joint. This helps the joint to move smoothly, but also distributes nutrition needed by the cartilage.
It is because of these important functions, that I believe in saving the menisci as far as possible, when it tears.
The basic anatomy of menisci
The medial meniscus is C-shaped and sits on the inside of the knee. The two ends of the C-shape are known as horns.
One horn is attached to the tibia in close relation to the anterior cruciate ligament (ACL), while the other horn is attached in close proximity to the posterior cruciate ligament (PCL).
The lateral meniscus sits on the outside of the knee and both of its horns are attached by ligaments to the tibia. It covers around 70% of the lateral tibial plateau – or in simple terms, the top part of the shinbone. The lateral meniscus moves around in the knee joint, more so than the medial meniscus does.
Only around 10 – 30% of the outer parts of the medial meniscus and 10 – 25% of the periphery of the lateral meniscus receive direct blood supply.
The importance of the anatomy of the menisci will become clearer in our next article, where I explain the different types of meniscus tears and injuries and how we diagnose and treat them.
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