A meniscus tear is a common injury for both active and older persons

The two menisci of the knee (the white crescents) act as a cushion between the femur and tibia, so that the two bones don’t rub against one another. — Wikimedia Commons

Your knee joint is made up primarily of two bones: the femur in your thigh and the tibia in your lower leg (shin).

There is also the kneecap, or patella, which sits in front of your knee to protect it from injuries that come from the front.