A meniscus is a piece of cartilage found where two bones meet (joint space). Menisci (plural of meniscus) protect and cushion the joint surface and bone ends. In the knee, the crescent-shaped menisci are positioned between the ends of the upper (femur) and lower (tibia) leg bones. The menisci protect the joint surface and absorb the shock produced by activities such as walking, running, and jumping.