What is a torn meniscus? The ends of the three bones in the knee--the femur, tibia, and patella--are covered with cartilage (a smooth material that covers bone ends of a joint to cushion the bone and allow the joint to move easily without pain) that acts as a shock absorber. Meniscus tears can occur during a rotating movement while bearing weight, such as when twisting the upper leg while the foot stays in one place during sports and other activities.