A meniscus tear is a common injury to the cartilage that stabilizes and cushions the knee joint. The pattern of the tear can determine whether your tear can be repaired. Radial tears sometimes can be repaired, depending on where they are located. Horizontal, flap, long-standing, and degenerative tears-those caused by years of wear and tear-generally cannot be repaired. If you have a tear in the white zone of the meniscus, surgery usually isn't done, because the meniscus may not heal. But surgery may be done if torn pieces of meniscus are causing pain and swelling.