A medial meniscus tear is an injury to one of the cartilages that support the knee, according to MedicineNet. The medial meniscus is a C-shaped piece of cartilage that is found at the top of the tibia, which is a long bone in the leg.
The medial meniscus is specifically on the inside of the knee joint, states Cedars-Sinau. The cartilage can be torn because of a sudden twisting of the knee, claims MedicineNet. A person with a torn meniscus experiences pain and swelling at the knee. He may also hear a popping sound when the injury occurs. In severe cases, the knee may give way altogether.