What is the meniscus and why did it tear?

The meniscus is a cartilage gasket or disc between the two bones in your knee, the femur (thigh) and tibia (shin). There are actually two menisci in each knee one on the medial or inner side of the knee and one on the outer or lateral side of the knee. They serve as a shock absorber in your knee and help with bending and twisting motions in the knee. The meniscus also protects the articular cartilage on the end of the bones in your knee from wearing down and turning into osteoarthritis. Because the medial meniscus is attached to other structures of the knee, medial meniscus tears are more common than lateral meniscus tears.

But I didn’t injure my knee!

A lot of patients come to my clinic complaining of pain in their knee, the most common cause is from meniscus tears. How did they tear the meniscus and why does it hurt? The meniscus acts with the motions of your knee to protect the articular cartilage on the bones of your knee. Sometimes patients know when they injure their meniscus, for example a young athlete who does repetitive twisting and squatting activities like soccer. However, I also see a lot of meniscus tears in patients who don’t really remember an injury but develop pain slowly over time. Often these patients are weekend warriors that have accumulated stresses and strains over a lifetime of activities involving their knees. This slow wear and tear process on the cartilage of the knee eventually tears the meniscus. This actually may be a more frequent type of torn meniscus called a degenerative meniscus tear. Meniscus tear symptoms may flare up from a simple deep knee bend to squat down and pick something up from the floor or stumbling and catching your fall.

Why does it hurt?

Whatever the mechanism, most patients will feel pain. If the injury is acute there may also be swelling and stiffness soon after the injury. These tears may settle down after a few days of rest, ice, compression, and elevation. Studies reveal that the meniscus actually doesn’t have much feeling in it so the pain actually comes from your body’s response to the tears. Often there is a flap or displacement of the injured meniscus cartilage that gets caught between the bones and irritates the lining of your knee where the nerve endings cause pain. Then your body pumps fluid into the knee to swell it up making it stiff and preventing you form moving too much and doing further damage to your knee. It is sort of a self protective mechanism. Isn’t that smart design? For patients that develop a torn meniscus from simple wear and tear over time there may not be a sharp pain or swelling but they may notice a dull ache develop over time, often it will be around the side and back of the knee. These patients may feel stiff in the morning, and have pain that waxes and wanes depending on their activity.

While many patients need to consider rest and time when they tear a meniscus, if the symptoms keep you from doing what you need to do or want to do, then meniscus surgery should be considered. I will cover meniscus surgery in another post.