Synonyms in a broader sense
Cartilage disc, anterior horn, pars intermedia, posterior horn, inner meniscus, outer meniscus,
Definition
The inner meniscus is – together with the outer meniscus – a part of the knee joint. It serves as a sliding and displacement bearing between the bones involved. Due to its anatomy, it is much more frequently affected by (sports) injuries than the outer meniscus.
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 together perfectly (they are therefore incongruent), the menisci are necessary in order to optimize the articulation (interaction) of these two surfaces and to distribute the strong forces that act here optimally. They therefore lie on the tibial condyles (joint gnardles of the tibia) as a kind of “socket”. When the knee joint is flexed, they slide backwards by up to one centimeter, only to return to their original position when stretched. This strong tensile and compressive load explains the susceptibility (at least of the inner meniscus) to injuries.
Anatomy and function of the inner meniscus
The inner meniscus is relatively exactly C-shaped and larger than the outer meniscus. It is anchored at its front and rear ends (anterior and posterior horn) in the bone, in the so-called area intercondylaris (area between the joint gnarls). It is also laterally fused with the joint capsule.
In addition, the inner meniscus is also fused with the inner ligament (medial collateral ligament or collateral ligament, Lig. collaterale tibiale). As a result of this fixation, it is more restricted in its mobility than the outer meniscus and thus comes under greater tension during knee movements. The inner meniscus is most severely strained during external rotation of the flexed knee.