The meniscus is a crescent-shaped structure composed of cartilage that functions to distribute body weight evenly across the three bones that make up the knee joint: the thigh bone, shin bone, and knee cap. The surfaces of these bones are covered with cartilage, which allows the bones to move smoothly against each other without causing damage to the bone.
Each knee has two menisci, which are located between the cartilage surfaces: one is on the inside of the knee (medial meniscus) and the other is on the outside of the knee (lateral meniscus). The menisci also cushion any impact between the thigh bone and shin bone when walking, jumping, or running. If the meniscus is damaged, body weight will be distributed unevenly, forcing unequal stress to the thigh and shin bones.
Small blood vessels provide nourishment to the meniscus, but there is also a large portion in the center of the meniscus that has no direct blood supply. If the meniscus is injured, this area of the cartilage often fails to heal because nutrients cannot reach it.