Meniscus
Introduction:
The word menisci are derived from the Greek work meniskos, which means “crescent”.
At knee joint the menisci plays a major role in congurency of the joint. Menisci forms the concavity in which the femoral condyles sits.
Meniscus of Knee:
There are two menisci in the space between the femoral and tibial condyles.
Medial meniscus.
Lateral meniscus.
They are crescent-shaped lamellae, each with anterior and posterior horn, and are triangular in cross section. The surface of each meniscus is concave superiorly, providing a congruous surface to the femoral condyles and is flat inferiorly to accompany the relatively flat tibial plateau.
Location:
Menisci rests between the thigh bone femur and the tibia and there are two knee joint ligaments. They are a type of cartilage in the joint. The rubbery texture of the menisci is due to their fibrocartilagenous structure. Their shape is maintained by the collagens within them.
Medial meniscus:
Anatomy and attachment
The medial meniscus is approximately 1.4 in (3.5cm) in length. The anterior horn of the medial meniscus is attached to the anterior surface of the tibia well off the tibial plateau.
The anterior fibers of the anterior cruciate attachment merge with the transverse ligament, which connects the anterior horns of the medial.
The posterior horn of the medial meniscus is firmly attached to the posterior aspect of the periphery to the joint capsule.
At its midpoint, the meniscus is firmly attached to the femur and tibia through a condensation in the joint capsule known as the deep medial ligament.
The medial meniscus has no direct attachment to any muscle, but indirect capsule connections to the semimembranosus may provide some retraction of the posterior horn.
Medial menisci are C shaped wedge fibrocartilagenous structure located between condyle of femur and tibia. It is somewhat more in C shape as compared to lateral menisci as it is medial meniscus are clear of the plateau anteriorly and posteriorly.
Anteriorly, it is also attached to lateral menisci by transverse ligament and patella either directly or by patellomeniscal ligaments which are anterior capsular thickenings. Its anterior portion is much narrower than the posterior portion and the narrower portion is less prone to injury also.
Lateral meniscus:
Anatomy and attachment
The lateral meniscus is almost circular and covers a larger portion of the tibial articular surface than the medial meniscus. The lateral meniscus is consistent in width throughout its course.
The anterior horn of the lateral meniscus blends into the attachment of the anterior cruciate ligament, whereas the posterior horn attaches just behind the intercondylar eminence, often blending into the posterior aspect of the ACL.
There is no attachment of the lateral meniscus to the LCL.
Its peripheral attachment is interrupted posterior to where the popliteal tendon passes. The capsular components attach the lateral meniscus to the tibia less firmly than the medial meniscus.
The lateral meniscus is more mobile than the medial meniscus and has a range of movement that may be as great as 10 mm (0.4 in) in an anteroposterior direction. This mobility is explained by the close proximity of the attachments of the anterior and posterior horns and the lack of attachment to the capsular ligament posterolaterally.
The firm attachment of the arcuate ligament to the lateral meniscus and the attachment of the popliteus muscle to both the arcuate ligament and meniscus ensure the dynamic retraction of the posterior segment of the meniscus during internal rotation of the tibia on the femur as the knee begins to flex from its fully extended position.