The meniscus is a tough, rubbery pad between the shinbone (tibia) and thighbone (femur) in the knee joint. There are actually two menisci inside the knee. The C-shaped medial meniscus is on the inside part of the knee, closest to your other knee. The U-shaped lateral meniscus is on the outer half of the knee joint.
The meniscus protects the knee by spreading out pressure and forces on the knee. Without it, these forces are concentrated to a smaller area, which puts more wear and tear on the joint. The meniscus also improves knee stability by forming a socket on the top surface of the tibia. This socket gives added support where the femur bone joins the knee.