Meniscus (anatomy)

As the meniscus (plural:. Menisci, Latinized meniscus / menisci, from the Greek μηνίσκος mēnískos = moon -shaped body, vkl Mene = moon ) is called in the anatomy of a disk-shaped ( in the knee crescent-shaped ) cartilage in a joint. Unlike a discus, a meniscus divides the joint cavity incomplete. In mammals, there are two major menisci in the knee joint as well as other joints (such as interphalangeal ) numerous small menisci, which often derived from the capsule and extend into the joint. The name derives from the Greek and means roughly half-moon. Even in birds menisci in the knee joint and other joints before ( ulnar joint, wrist, spine).

Function

Both calculations (FEM ) and laboratory measurements underline the importance of Kniegelenkmenisken in the (pressure) force transmission between the two joint surfaces (of the femur and tibia ) of the knee joint. The Kniegelenksmenisken consist mainly of collagen fiber ( about 90 %), absorb the tensile forces. Tensile forces occur especially in the vicinity of the front and rear horns which short tapes anterior (front) and posterior ( rear) anchored to the tibial plateau, are attached. Additional tensile stress arises in the deformation of the menisci eg squats. In addition to these basic types of stress, it is very likely due to the shape of the menisci that they also ensure a better distribution of synovial fluid in the joint cartilage to reduce friction and nutrition.

The fact that people with a surgically resected meniscus significantly increases the risk of early osteoarthritis, is known since 1948 and widely recognized today. Due to the mobility of the menisci (especially of the lateral meniscus ), they also increase the articular surface on the tibial plateau or the contact surface for the head of the femur. By the joint shape ( Bicondyläres joint) of the knee are here, in addition to pure bending and stretching movements, rotations, by a few degrees, which is enforced in full extension in the intact knee joint as so-called final rotation and displacements (translations ) of the front and the back. The contact surface of the bony tibial plateau would be unsuitable for this purpose without the menisci.

Damage to the meniscus apparatus

From injuries to the menisci athletes are mostly affected or people whose activity overstressed the knee, such as tiler. Special risk sports for meniscus injuries include football, fencing, tennis, handball, skiing, snowboarding, squash, basketball, discus, javelin, skateboarding, rugby, karate and cycling ( due to an accident ). A meniscus injury usually occurs with a rapid rotation (~ rotation of tibia and femur about the longitudinal axis ) of the knee joint as well as during rapid flexing or stretching (~ movement about the transverse axis). The free edge of the meniscus falls during these movements between the joint body and tears thereby partially or completely on ( bucket handle tear ).

Discoid meniscus

The discoid meniscus is a congenital malformation of the Kniegelenksmenisken. It can lead to a snap - phenomenon and pain that typically start with the sixth to eighth year.

Meniscus bruise

The harmless variant of a meniscus (injury ) is called the meniscus bruise. Here is sufficient conservative treatment and a sports break of about three weeks. Operationally can help in some cases the cure here is a relief cut.

Meniskusruptur

The situation is different ( Meniskusruptur ) at a meniscus tear. Medial meniscus injuries ( ie, the medial meniscus ) are significantly more likely than those of the lateral meniscus. The cracks are classified according to their course of direction in the longitudinal crack, Radiärriss or inclined cracks ( crack lobe ). With regard to the spatial plane, a distinction is vertical cracks and horizontal cracks. Special forms are complex cracks, the bucket-handle tear and a "flipped meniscus ". Diagnosis is made by clinical examination, MRI and arthroscopy ( arthroscopy ).

A bucket-handle tear is the designation for a parallel to the main direction of the fibers extending meniscus tear. The meniscus is thereby split along its course along which front and rear ends of the fragment continues to maintain connection to the rest of the meniscus. The free edge moves into the joint space, causing acute pain and joint movement, the quite unexpected block.

Degenerative changes

Just as the cartilage surface of a joint degenerative changes over time, wear the menisci. Under load the meniscus tissue is rolled out, is getting thinner until it finally tears. These changes are collectively referred to as Meniscopathie and are a part of the action in the development of osteoarthritis. In case of accident injuries that should be considered as work-related accident, the histological examination of the meniscal tissue is crucial for the recognition of an accident context. Other degenerative changes can also be caused by an eversion angle other than zero degrees.

The current standard method for treating degenerative changes in the meniscus - arthroscopic partial meniscectomy - was recently reviewed in a study on the effectiveness. The study showed that the operation after one year of no advantage to a sham operation. This is consistent with some existing similar studies.