ACL Solutions - The ACL - Torn Meniscus

Associated Injuries

The weight bearing surfaces of your knees are covered with articular cartilage. There are also two "shock absorbers" in your knee on either side of the joint. These two structures are called the medial meniscus and the lateral meniscus. The menisci are horseshoe-shaped pieces of cartilage that help to center the knee joint during activity and minimize the amount of stress on the articular cartilage. The combination of the menisci and the articular cartilage in your knee produces a nearly frictionless gliding surface.

Studies show that when the ACL is torn approximately 50% of patients also tear their meniscus at the same time. If a part of the meniscus is torn, it can cause a significant amount of pain. The lateral meniscus is more commonly injured than the medial meniscus. Some tears in the meniscus can heal themselves, others may require surgical treatment to help them heal, and some meniscal tears create fragments that need to be removed.

Intact and torn meniscus (Image credit: Seif Medical Graphics)

This illustrates the normal position of the menisci on the weight bearing surface of the tibial plateau. In the figure on the left, the medial and lateral menisci are seen on either side of the tibia. In the figure on right, there is a tear in the lateral meniscus.

Torn meniscus repaired with sutures and tacks (Image credit: Seif Medical Graphics)

Certain meniscal tears can be repaired. The ability to repair meniscal tears depends upon the type of tear, how long the meniscus has been torn, and how old the patient is. In general, younger patients with tears that are near to where the meniscus attaches to the capsule of the knee joint are better candidates for a meniscal repair than are older patients who have a tear that creates a free flap of meniscus. Meniscal tears can be repaired with either sutures, or special tacks that can be inserted arthroscopically.

Torn meniscus removed (Image credit: Seif Medical Graphics)

Certain tears and certain patients are best treated with removal of the torn part of the meniscus. In this situation, special instruments are used to removed the damaged portion of the meniscus while preserving as much healthy tissue as possible.

Blood supply and the rationale for debridement versus repair

Blood supply of the meniscus (Image Credit: Seif Medical Graphics)

In this picture, a slice of the meniscus is seen under a microscope. The blood supply for the meniscus enters at the junction between the edge of the meniscus and the capsule of the knee joint through a rich network of capillaries that do not extend very far into the meniscus. Tears that occur in parts of the meniscus that have a good blood supply have a much better chance of healing, whereas those that occur in the inner parts of the meniscus are less likely to heal and are better treated by removing the torn piece of tissue.

What happens when the surface cartilage is damaged at the same time?

Many patients will also slightly damage the surface cartilage inside their knee when they tear their ACL. This type of damage can be superficial and it can also be quite deep. The depth and the amount of damage to the surface cartilage determine how the surgeon can repair the cartilage. Very shallow areas of damage can be smoothed out with a special tool called a "shaver", however, very deep areas of damage that go down to the bone underneath the surface cartilage are more difficult to treat. Areas of deep damage can be repaired in a number of different ways. One way is to drill several small holes into the bone in order stimulate the bone to produce a new layer of surface cartilage. Another way to fix the damage is to take a piece of healthy cartilage from somewhere else in your knee and use it as a graft to fill the defect.

When the ACL is ruptured the medial or lateral collateral ligaments can also be injured. The medial and lateral collateral ligaments stabilize your knee from side-to-side. The most common collateral ligament that is injured at the same time as the ACL is the medial collateral ligament. Unlike the ACL, this ligament will usually heal on its own, without surgery. When another ligament is injured along with the ACL, it usually makes it more important to reconstruct the ACL because the two injuries combined can make the knee very unstable.

Some people who tear their ACLs and also injure the surface cartilage or the menisci will have more pain and problems as a result of these other injuries than from the torn ACL. In some situations, surgery is performed in order to repair damage to the surface cartilage or the menisci without actually fixing the ACL.