With age and repeated minor traumas a knee meniscus may degenerate and much of its shock-absorbing function may be lost.
The normal meniscus is comprised of a cartilage-like matrix, containing relatively few cells which are suspended in the matrix, and which produce the collagen and proteins that give it structure. Circumferential collagen fibres provide most of its strength, but fibres are also arranged in several directions to allow for absorption of the load when a person walks.
Blood vessels supply the outer rim, but there are no blood vessels in the inner rim, which depends on the joint fluid for nutrition. The normal nerve supply is to the outer rim and to the horns of these crescentic structures.
With age, the meniscus integrity may be compromised and random tears appear in the mid-body and the posterior horns, associated with damage to the cartilage which normally covers the end of the femur and tibia in the joint.
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