The meniscus is the fibrocartilage pad between the femur and tibia that absorbs shock
A twisting injury can cause the meniscus to tear, there may or may not be swelling. A symptomatic tear can cause the knee to lock or buckle. The mcmurray maneuver is the classic test for meniscal tears but tenderness at the joint line can also help with the dx. A ligament exam should also take place.