Meniscus Injuries - Softening the Blow

It’s the substance in the knee that acts as a cushion between the thigh bone and the leg bone. That’s the meniscus described in a nutshell. Well, far from that, the menisci is actually a complex structure that plays a vital role in the knee joint.

So where exactly is the meniscus positioned? Well, firstly, there are two menisci (the plural for meniscus). They are both attached to the articular surface of the tibia (the leg bone) in the knee. The medial meniscus in on the inner part of the knee, the lateral on the outer. Both menisci have their distinctive shapes. The lateral meniscus is shaped more like a circle and cover a larger surface area whereas the medial meniscus is more C-shaped.

The menisci play an integral role in contributing to the stability of the knee joint as well as transmitting forces through it. The end of the femur bone that makes up the upper part of the knee is somewhat hemispheric in shape, while the upper part of the tibia is generally a flat surface. One could imagine that a round object rolling and gliding on a flat surface isn’t all that stable. This is where the menisci come into play. They act to increase and improve contact between the femur and tibia cartilage surfaces.

Because the meniscus is a more elastic structure compared the cartilage around the tibia and femur bones, it absorbs forces through the knee better. The shape of the meniscus that increases joint congruity and the composition of the meniscus that improves shock absorption both play important roles in transmitting forces. In cases whereby there is a loss of the meniscus as a result of injury, there is a significant increase in peak pressure between the femur and tibia bones. This in turn will lead to faster wear of the cartilage surfaces and eventually knee osteoarthritis.

Injury to the meniscus can occur as either a result of an acute injury like in a fall or a sports injury as well as a result of a more chronic/longstanding issue. Very often, in the setting of an acute trauma like that of a sports injury, the patient tends to have an ACL tear with a concomitant injury to the lateral meniscus whereas chronic injuries tend to involve the medial meniscus.

So what kind of symptoms might one experience when there is an injury to the meniscus? Well, as stated above, meniscus injury can occur concomitantly with other injuries to structures in and around the knee like the cartilage and ligaments. While meniscus injury present with only pain in most cases, one must take into consideration that other structures may also be injured and contribute to other symptoms.

Occasionally, in cases of a more severe tear, the meniscus might get displaced and get jammed in between the gliding femur and tibia bones. This then leads to the knee being locked into a certain position. This condition is termed locked knee. As mentioned above, apart from its role in transmitting forces, the menisci is also an important stabiliser of the knee. They become primary stabilisers of the knee when there is deficient function of the knee ligaments. So while pain is still the main symptom in meniscus injury, the symptom of knee instability should also be considered. To be more precise, conditions called ramp lesions and root tears contribute to most cases of instability in cases of meniscus injury.

Diagnosis of meniscus injuries can be made from patients’ history and examination. A MRI will offer a very good indicator to the exact location and pattern of tear of the meniscus, as well as being able to detect other concomitant injuries. Treatment usually starts with a period of physiotherapy but very often requires surgery to address the tears. Minimally invasive surgery using an arthroscope is the mainstay of treatment. Specialised sutures are used to repair them. However, in more complex tears, repair may not be suitable, thus the meniscus will be trimmed in such cases. Whenever possible, it is integral that the meniscus is repaired and preserved, because, as we have read above, they quite literally soften the blow to the knee.