Synonyms in a broader sense
lateral meniscus English: meniscus
The outer meniscus is – together with the inner meniscus and the cruciate and collateral ligaments – part of the knee joint. It improves the ability of the joint surfaces to fit together and ensures an optimal distribution of pressure. Because it is not fused with the collateral ligament – in contrast to the inner meniscus – it is less under tension during movements and is therefore very rarely affected in the event of injuries.
Anatomy and function of the menisci
The menisci of the knee consist of fibrous cartilage. They lie within the knee joint, which is formed by the joint cartilage (condyles) of the thigh bone (femur) and tibia (tibia) and the kneecap (patella). They lie – viewed from the front – like two wedges in the knee joint, with the base being on the outside and becoming narrower towards the inside.
Seen from above, they have an approximate C-shape. Due to the relatively small contact surface between the thigh and lower leg bones, which do not fit perfectly together (they are therefore incongruent), the menisci are necessary to optimize the articulation (the interaction) of these two surfaces and to distribute the strong forces acting here in an optimal way. They therefore lie as a kind of “socket” on the tibial condyles (joint gnardles of the tibia). When the knee joint is flexed, they slide backwards by up to one centimetre, only to return to their original position when stretched. This strong tension and pressure load explains the susceptibility (at least of the inner meniscus) to injuries.
Anatomy and function of the outer meniscus
The outer meniscus is more strongly curved than the inner meniscus, it has – except for an opening to the inside – almost O-shape. It lies on the outer half of the tibia plateau (tibial joint surface). There the outer meniscus is anchored to its anterior horn and its posterior horn in the tibia, more precisely in the area intercondylaris (i.e. the area between the joint gnarls).
In addition, the posterior horn of the outer meniscus is attached to the inner surface of the medial femoral condyle (inner joint gnarl of the thigh) by a ligament, the Ligamentum meniscofmorale posterius (also called Wrisberg ligament). It therefore pulls upwards at an angle and starts immediately behind the posterior cruciate ligament (Ligamentum cruciatus posterius). Although the meniscus is fused with the joint capsule, the latter is relatively thin on the outside.
In addition, the outer meniscus – in contrast to the interior – is not fused with the collateral ligament (Ligamentum collaterale laterale). Therefore it is much more mobile. This also means that it is not under as much tension during movement as the inner meniscus. Therefore it is only in the rarest exceptional cases affected by injuries.