When you sustain a knee injury, you damage one of the four major ligaments found in your knee. The most common injury I see is torn cartilage, also known as your meniscus. More serious injuries involve medial collateral ligament (MCL), the anterior cruciate ligament (ACL), and less often the posterior cruciate ligament (PCL).
Usually occurs while changing direction rapidly.
Injuries to the MCL are usually caused by a direct blow to the outside of the knee.
The PCL is often injured when a worker receives a blow to the front of the knee or makes a simple misstep.
When people talk about torn knee cartilage, they are usually referring to a torn meniscus. The meniscus is a tough, rubbery cartilage that is attached to the knee's ligaments. The meniscus usually tears due to sudden twisting, jumping, or trauma to the knee. Physical contact is often involved.