The meniscus are important structures in the knee. They are pads or cushions that take some of the forces as they cross the knee joint. There are two in each knee, one on the inner side of the knee and one on the outer side. They are shaped like a crescent moon and fit partway between the two bones. The meniscus is made of a tough gristle-like tissue. It has a blood supply only at its outer edge where it attaches to the remainder of the knee.
A meniscus can be torn by injury or sometimes can develop tears from wear. Tears can occur in different patterns and in different locations in the meniscus. Symptoms are usually pain and sometimes a catching or locking sensation about the knee. They can cause swelling as well.
A meniscus tear can be suspected by the story and exam and is usually confirmed by an MRI scan. Arthroscopic surgery is often performed to address a meniscus tear. In the majority of cases, the tear is in an area of the meniscus that does not have blood supply. This means it does not have the ability to heal, so the torn portion is trimmed so it does not flap about in the joint. On some occasions the tear is where there is some blood supply, so it may have the potential to heal. In these cases, the tear may be repaired with stitches allowing it a chance to heal.
Many patients with arthritis develop meniscus tears from the “wear and tear” process of arthritis. In these cases, the meniscus tear may not be the main problem but a part of the arthritic degeneration of the knee. Arthroscopy to treat the meniscus tear may not offer much relief.
Since the meniscus serves to absorb stresses across the knee, if a tear has resulted in a significant amount of meniscus not performing its function, the increased stresses can lead to arthritis in that part of the knee. If a patient is young, this is of particular concern because of the many years they have left to use that knee. Meniscus transplantation can be performed in some select cases to try to restore the cushioning effect of the meniscus. In his fellowship, Dr. Steensen worked with one of the pioneers of meniscus transplantation, and co-authored one of the first reports on meniscus transplantation.