A meniscus is one of two half-moon shaped discs of specialized cartilage lying between the femur and tibia with more secure attachment to the tibia. The two menisci (lateral, or outside, and medial, or inside), serve several functions. These functions include: adding in joint lubrication, articular cartilage nutrition, stability and distribution of forces between the femur and tibia. 
The meniscus may be injured when the knee is bent or twisted while bearing weight. Meniscal injury or degeneration can also be a result of overuse over time. For example, repetitive squatting or kneeling can cause meniscal wear and make it more likely to tear. Meniscal tears often accompany tears of the ligaments within the knee, most frequently the Anterior Cruciate Ligament.
more
more