Meniscus - anatomy and diseases

The meniscus is a cartilage in the knee joint that ensures that the joint is supported during flexion and extension. It reduces the friction surface and acts as a shock absorber.

What is the meniscus?

Meniscus is the correct anatomical term for a crescent-shaped cartilage in the knee joint. In the knee, there is both an inner meniscus (medial meniscus) and an outer meniscus (lateral meniscus). These fibrous cartilages are referred to in their entirety as menisci.

The sickle-like lateral meniscus consists of three sections:

• Anterior horn (Cornu anterius),
• middle section (pars media)
• posterior horn (posterior cornu)

The outer meniscus is attached to the upper and front part of the tibia via the anterior horn, whereas the posterior horn is attached to the back of the tibia. The inner meniscus can also be divided into the anterior horn, middle section and posterior horn.

The inner cartilage is fused to the inner collateral ligament of the joint capsule and is therefore not as mobile as the outer meniscus.

What is the function of the menisci?

The menisci have several functions. For example, the smooth cartilage surface of the structures reduces the friction that occurs between the joint head and socket during movements in the knee joint. At the same time, the menisci act as shock absorbers and cushion movements within the knee joint. This function is particularly important when the knee is subjected to heavy loads, for example during sporting activities.

The inner and outer meniscus also ensure that the joint surfaces of the femur and tibia fit together exactly. As a result, weight and pressure on the knee joint are better distributed. The menisci also ensure good nutrition of the cartilage tissue by optimally distributing the synovial fluid on the joint cartilage.

What diseases can affect the meniscus?

Injuries to the menisci mostly affect athletes. In addition to skiing and snowboarding, high-risk sports include tennis, handball and karate. People who often overuse their knees at work are also more frequently affected by meniscus injuries. Meniscus contusions and tears of the menisci are among the most common meniscus lesions, with the inner meniscus tearing much faster than the outer meniscus.

Just like all cartilaginous joint surfaces, the menisci can also be affected by signs of wear . The meniscus tissue degenerates, becomes thinner and thinner and eventually tears. Such meniscopathies occur in particular in the context of osteoarthritis, i.e. joint wear and tear.

In contrast to this acquired damage, the so-called disc meniscus is a congenital malformation. This anatomical variant of the menisci, which sometimes occurs on both sides, leads to pain and the snapping phenomenon in the knee joint.

How are meniscus diseases diagnosed?

Various tests are available if a meniscus injury is suspected. These include, for example, the Apley, McMurray and Payr tests, in which the doctor moves the lower leg and thigh in different variations. Depending on whether pain occurs when the inner or outer meniscus is stressed, the doctor can draw conclusions about damage to the corresponding structure.

During the physical examination, the doctor also checks whether there is joint effusion. If the suspicion of meniscus disease is confirmed, magnetic resonance imaging (MRI) can be used for further diagnosis. Magnetic resonance imaging can be used to visualize the ligaments, menisci and muscles of the knee in a cross-sectional image. While lighter spots indicate cartilage wear, a light-colored stripe indicates a tear.

Arthroscopy is also suitable for taking a closer look at the knee joint and therefore also the menisci. Here, the doctor inserts a small camera into the knee joint through an incision in the skin.

X-ray and ultrasound examinations can also be useful in the diagnosis of meniscus diseases.

Specialists for the treatment of meniscus damage

Meniscus surgery is used for the surgical treatment of meniscus damage. In the case of major or irreparable damage, it is also possible to have a meniscus implant (artificial meniscus) inserted. Specialists in the treatment of meniscus damage are specialists in orthopaedics and trauma surgery, particularly those with further training and specialization in the field of knee surgery.