Menisci are pads of cartilage that fill in the space between the thighbone (femur) and shinbone (tibia). They help stabilize and cushion the knee joint. The lateral meniscus is located on the outer side of the knee. The medial meniscus is located on the inner side of the knee.

The medial meniscus is most commonly damaged when people have their weight on a foot and their knee twists forcefully. The medial meniscus can be damaged when the knee is hit from the side. In such cases, the anterior cruciate and medial collateral ligaments are often also damaged.