A meniscus tear is damage to one of the rubbery discs that cushion your knee joint. It's usually caused by twisting your knee while your foot stays planted on the ground. It can be painful and keep your knee from working right.
Some tears will heal with rest and physical therapy. Others need to be repaired with surgery.
Where a meniscus tear occurs is one of the most important things that affects healing. Tears at the outer edge (red zone) tend to heal well because there is a good blood supply. The inner area (white zone) lacks a good blood supply and therefore does not heal well.
The type of tear often determines whether a tear can be repaired. Longitudinal tears are often repairable. Radial tears may be repairable depending on where they are located. Oblique (flap) tears and another type called horizontal tears are generally not repairable.