The knee meniscus is a special layer of cartilage that lines the knee joint. As in every joint, there is a think layer of articular cartilage, but due to the huge forces that go through the knee, it needs something extra.
The knee menisci are two portions of thick, rubbery tissue that line the joint. They sit on the top surface of the tibia (shin bone) in 2 crescent shaped parts, the medial meniscus (on the inner side) and the lateral meniscus (on the outer side). The medial side is the larger of the two.
Here we will look at the role of this special knee cartilage, how it gets injured and what we can do to keep it healthy.
The knee mensicus is really important as it:
1) Helps the tibia and femur to fit better to each other (increases
surface area contact by 40-60%), making the joint more stable
2) Provides a smooth surface between the femur and tibia, preventing bone rubbing on bone
3) Helps ensure correct weight distribution between the tibia and femur
4) Act as shock absorbers/cushions reducing the force going through the knee bones
5) Contains nerves which help improve balance and stability
There are two ways that the knee meniscus gets damaged:
1) Injury: The menisci are often injured when the knee twists suddenly eg when playing sports or during a fall. This tends to tear part of the cartilage and can cause bleeding in the joint resulting in swelling
2) Wear and Tear: As we age, our cartilage becomes more brittle and can start to wear away. This also makes them more prone to injury. This is a common feature of arthritis
Meniscal tears can occur in any part of the cartilage (as shown in the diagram) and can take a long time to recover from. Small blood vessels feed the outer edges of the meniscus but the middle parts have no direct supply which means it is very slow to heal following injury
One of the most common signs of a meniscal tear is locking - where the knee gets stuck. This happens which a flap of torn knee meniscus gets stuck in the joint block movement. By wiggling your leg around, you can usual move the flap out of the way, but the problem will keep occuring. If this is the case, arthroscopic surgery will be advised to trim the flap.
To find out more about knee cartilage injuries, visit the meniscal tear section.
We are all born with different quality knee cartilage which we can’t change, but we can help keep it healthy by ensuring that the muscles around the knee are strong so that less force goes through the knee meniscus. The best way to do this is by doing knee strengthening exercises.