The meniscus is a piece of cartilage in your knee that cushions and stabilizes the joint. It acts as a shock absorber, protecting the bones from wear and tear. Each of your knees has two pieces of this cartilage:

The medial meniscus is on the inside of the knee.
The lateral meniscus sits on the outside of the knee.
Both are shaped like Cs and provide cushioning between your shinbone (tibia) and your thighbone (femur). The two menisci help to keep your knees stable.