How do meniscal tears happen?
Although the meniscus can become degenerate with age, usually a tear is a result of an injury.
This may be a blow on the side of the knee, or a non-contact injury like twisting the body while the foot is on the ground, such as kicking a ball.
"Not all meniscal tears are correctly attributable to an acute injury: degenerated meniscal cartilage may fail under simple load conditions. By contrast, resilient meniscal tissue will tear only with substantial trauma."

