All about Meniscus and Meniscal Injuries
The meniscus is a fibrocartilage component of some synovial joints. The menisci (commonly referred to as cartilage) of the knee are the most widely known examples. Another joint containing fibrocartilage is the A-C joint. This discussion will be concerned with the knee.
The menisci of the knee have unique shape. They are a wedged, ?C? shape. The ?C? shape corresponds to the surface area of the femur that would contact the surface of the tibia if the menisci were not present. The wedge shape corresponds to the shape of the heads of the femur as well. The ends of the femur are rounded for maximal flexion of the knee. The menisci act like a wedge to assist with the rotational stability created by the anterior cruciate ligament; like a wooden block placed behind the wheel of a car prevents the car from rolling.
The menisci also act as a shock absorber. As we walk, run, and jump the knee absorbs tremendous forces. The menisci help to absorb these forces so that the joint surfaces are not damaged. The compressive forces on the knee have been described as equivalent to the ?amount of compression that would be exerted on the skin if a 300 pound person would hang from a ledge by a fingertip.? The amount of force increases exponentially as the speed of movement increases from walking to running to jumping. The menisci disperse the compressive forces over the entire knee rather than isolating them.
Mensical blood supply is limited: the menisci get nutrition from blood and synovial fluid. The outside border (red zone) of the meniscus has a blood supply that proliferates from the synovial capsule while the inside border (white zone) gets its nutrition from the synovial fluid. Due to this tears nearer the middle of the knee (white zone) do not heal due to a lack of blood supply to trigger an inflammatory response. Because of this many meniscal tears do not heal.
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