Meniscus Tears: Overview

Meniscus Tears: Overview

The meniscus is commonly referred to as a shock absorber for the knee. Each knee has 2 of these C-shaped structures: the medial meniscus on the inside of the knee and the lateral meniscus on the outside of the knee, providing a cushion between the thigh bone, or femur, and the shinbone, or tibia.

A meniscus is made up of mostly water with the rest being spongy connective tissue and proteins. This cross-section view of the meniscus shows how the outer edge is thick while the inner edge is very thin. This helps provide stability to the knee, with the round end of the femur sitting on the relatively flat top of the tibia.

If the knee did not have the meniscus, there would be 50% more weight on the surface cartilage in the knee when it is completely straight, and up to 200% more weight when it is bent. This could lead to early arthritis.

How does the meniscus get injured? Typically, it is when the knee is being compressed, like when standing or running, and there is a twist at the same time. This compression and twisting causes tearing in the meniscus. There are many different sizes and patterns of meniscus tears. One of the more well-known types is the bucket-handle tear. This is when a long tear occurs but stays attached at the front and back and the torn piece can flip back and forth like a bucket handle.

About one-third of meniscus tears happen along with an ACL tear. Typically, younger athletic individuals suffer from traumatic tears that occurred due to an injury, while degenerative tears that slowly happen over time are more common later in life. It is difficult to completely prevent a meniscus tear from happening, but stretching and strengthening leg muscles can certainly help.

Some people may wear a brace if their knee already feels unstable or if they are recovering from another knee injury so that a secondary meniscus injury does not occur. Each meniscus is attached to the top of the shinbone in 2 places. The attachment in front is called the anterior root, and in the back is the posterior root. The attachments are very close to the ACL and PCL in the middle of the knee. These 2 attachments allow the rest of the meniscus to shift slightly as the knee bends and straightens.

When it comes to healing, the meniscus needs blood supply just like anything else. It is divided into 3 zones based on the amount of blood supply in each zone. The outer edge is the red-red zone with the most amount of blood supply or vascularity. This turns into the red-white zone, where the blood supply starts to decrease. The white-white zone takes up the majority of the meniscus, where the inner edge hardly gets any blood at all. As a result, tears toward the inner edge have a less chance of healing than those closer to the outer edge.

If a patient has a meniscus tear in their knee, the most common symptoms they will report are pain right at their joint line where the meniscus sits, clicking or catching of their knee when they do certain movements, and even an unstable sensation with walking or twisting. The health care provider will check to see if there is any swelling inside the joint. Unlike an ACL tear, it may take a few days for the knee to swell up after suffering a meniscus tear.

There are several special tests that are used to check for a meniscus tear. These tests are designed to reproduce the patient's symptoms, which can help lead the health care provider to make an accurate diagnosis. X-rays are taken to make sure there are no fractures and to check for any arthritis. Sometimes, full-length x-rays of the legs are taken to see if there are any alignment issues that are contributing to the problem.

Doing an ultrasound can give a pretty good picture of what is going on with the meniscus, but it really is best seen on an MRI, which is typically the best way to look at all soft tissue. The meniscus is highlighted here in both the side view and the front view of the MRI. In the top-down view, you can see there is a break in the normal C-shaped meniscus. This is where the tear is. Once a final diagnosis is made, the doctor and patient create a treatment plan so the patient has the best chance of returning to their desired activity level.