Meniscus Knee Injuries
A meniscus tear is a common knee injury that can happen to anyone in any age group. When someone talks about torn cartilage in the knee, they are usually referring to a torn meniscus.
What is the Meniscus?
The meniscus is a piece of cartilage between your femur (thighbone) and tibia (shinbone). There are two menisci in each knee joint.
- Medial Meniscus - The C-shaped cartilage on the inside part of the knee, closest to your other knee.
- Lateral Meniscus - The U-shaped lateral meniscus is on the outer half of the knee joint.
These two menisci act as shock absorbers in the knee. Forming a cushion between the shinbone and the thigh bone, they help spread out the forces that are transmitted across the joint. As the knee bends, the back part of the menisci takes most of the pressure.
By spreading out the forces on the knee joint, the menisci protect the articular cartilage from getting too much pressure on one small area on the surface of the joint. Articular cartilage is a smooth slippery material that covers the ends of the bones that make up the knee joint. Without the menisci, the forces on the knee joint are concentrated onto a small area, leading to damage and degeneration of the articular cartilage, a condition called osteoarthritis.
The menisci convert the surface of the shinbone (tibia) into a shallow socket, which adds stability to the knee joint. Without the menisci, the round thighbone (femur) would slide on top of the flat surface of the tibia.
Causes of Meniscus Tears
Meniscal tears can occur at any age, but the causes are somewhat different for each age group.
In younger people, the meniscus is a fairly tough and rubbery structure. Tears in the meniscus in patients under 30 years old usually occur as a result of a fairly forceful twisting injury. Often times, it is more likely to be caused by a sports activity.
Meniscal tears in people older than 30 often occur due to degeneration, which simply means that the meniscus grows weaker with age. Because of this, people of older ages often end up with a tear as a result of a minor injury, such as from the up-and-down motion of squatting.
Meniscus Tear Symptoms
The most common symptom of a torn meniscus is pain. The pain may be felt along the edge of the knee joint closest to where the meniscus is located. Or the pain may be more vague and involve the whole knee.
Most people can walk on their injured knee and many athletes continue to play with a tear. A few days after injury, however, the knee will gradually become more stiff and swollen.
Other symptoms of a meniscus knee injury may include:
- Feeling a “pop” when the injury occurs
- Stiffness and swelling due to the accumulation of fluid inside the knee joint (sometimes called water on the knee)
- Inability to completely straighten out the knee (known as locking of the knee)
A torn meniscus can cause long-term problems. The constant rubbing of the torn meniscus on the articular cartilage may cause the joint surface to become worn, leading to knee osteoarthritis.
To learn more about osteoarthritis of the knee, download our educational document A Patient’s Guide to Osteoarthritis of the Knee.
Diagnosis of Meniscus Tears
Diagnosis begins with a history and physical exam. Your doctor will try to determine where the pain is located, whether you've had any locking, and if you have any clicks or pops with knee movement.
It is likely that your doctor will also order imaging tests, such as an x-ray and/or MRI to help confirm the diagnosis.