Lateral meniscus of the knee: A thickened crescent-shaped cartilage pad in the outer portion of the joint formed by the femur (thigh bone) and the tibia (shin bone). The lateral meniscus acts as a smooth surface for the joint to move on. The lateral meniscus is toward the outer side of the knee joint. It serves to evenly load the surface during weight-bearing, and also aids in disbursing joint fluid for joint lubrication. See also knee.