Functional and Anatomic Characteristics of the Menisci

The menisci are intra-articular fibrocartilagenous structures which optimize the joint function1. They have a half-moon shape and present a wedge shape in the concave of its transversal section2. This shape could be seen since the eight week of the embryonic period3, presenting the adult characteristics at the 14th weeks, with a prominent vascularization and cellularity which will be decreased by the hand of maduration1. There is an abundant extracellular matrix which has a 70% of water, collagen type I, proteoglycans and elastin3 in which few cells (fibrochondrocytes) are embedded. With regards to its ultra-structural architecture, the great majority of bundles are circumferential which confers compression forces support. There are also radial bundles that give stability to the prior ones and help to support longitudinal tension. Finally, there is a superficial layer with a disorganize distribution which shares the stress (Figure 1). The menisci are inserted into the tibia through their horns (anterior and posterior) and periferically to the joint capsule. The medial menisci has little mobility in comparison to the lateral one due to anchors to the posterior oblique’s fibers of the medial collateral ligament. Tensile forces act into the menisci moving them to the periphery, making the longitudinal bundles of collagen support traction forces between both horns. Shear stress isn’t well tolerated, this fact explains the longitudinal injuries observed during childhood The menisci are stabilized by different ligaments such as: Winslow ligament (Figure 2), coronary ligaments and menisco-femoral ligaments (Wrisberg and Humphrey) (Figure 3). The Popliteal tendon also contributes, adding an anchor to the lateral menisci in its posterior border. The parameniscal plexus irrigates the menisci through branches from the superior, inferior, lateral and medial geniculate arteries in a radial direction from the periphery (Figure 4). At ten year old, the vascularization pattern is like in adulthood; in which, 10%-30% of the