The meniscus cartilage is like a shock absorber pad between the femur (thigh bone) and tibia (shin bone) in the knee. There are 2 menisci - 1 on the inside of the knee ("medial meniscus") and 1 on the outside of the knee ("lateral meniscus"). Actually many meniscal tears can and are successfully treated without surgery. Typically physical therapy (to strengthen the surrounding muscles) and anti-inflammatory medicines (i.e. Ibuprofen, to decrease inflammation and swelling) will be recommended initially for symptomatic meniscal tears.
One type of meniscal tear that will require surgery is a "bucket-handle" tear. This is a tear that usually occurs acutely and causes a "locked knee" where the knee gets stuck due to a large segment of the meniscus cartilage becoming lodged between the femur and the tibia. The 2nd type of meniscal tear that may require surgery is one in which the symptoms persist (pain and swelling and often prevention of performing activities and/or sports) despite appropriate non-operative treatment.
For those patients who require surgery, make sure you ask your doctor what the status of the surface cartilage is before the operation. The surface cartilage is also called articular cartilage and is like the white, glistening tissue on the end of a chicken bone. The loss of articular cartilage is what happens in arthritis and sometimes is damaged as well in patients with meniscal tears and can alter the treatment, rehabilitation, and ultimate outcome in patients having meniscal surgery.
Ultimately, arthroscopic treatment for isolated meniscal tears is highly successful in most patients.