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Meniscus injury

A torn meniscus can either be caused by an sudden injury to the knee (traumatic meniscus tear) or happen over time with increasing age (degenerative meniscus tear).

A torn meniscus can either be caused by a sudden injury to the knee (traumatic meniscus tear) or happen over time with increasing age (degenerative meniscus tear).

In each knee joint, there are two menisci, the inner (medial) and the outer (lateral). The menisci are crescent-shaped pieces of cartilage that provide the knee with stability and help distribute the load in the knee joint. The menisci are therefore very important for normal knee function. When a meniscus tears, the load transmission in the joint is affected, creating an uneven load on the articular cartilage. In the long run, this can contribute to an increased risk of developing osteoarthritis (OA).

Common amongst young athletes

A traumatic meniscus tear is most common amongst athletes and occurs either as an isolated injury or in conjunction with other knee injuries (most often together with an ACL tear). It is more common for the inner (medial) meniscus to tear as it is less moveable than the outer (lateral) meniscus.

Traumatic meniscus tears can create several knee problems such as pain, popping, or locking in the knee. As a result, a torn meniscus may occasionally require arthroscopic surgery (keyhole surgery) to either remove the damaged part of the meniscus (meniscal resection) or sew the damaged meniscus back together (meniscal repair). Arthroscopy is a surgical procedure that involves a surgeon making small incisions in the skin through which a camera and small instruments are inserted into the knee to perform the surgery.

Meniscal repair surgery is possible for certain types of traumatic knee injuries but can only be performed in cases where the blood-supplied part of the meniscus closest to the joint capsule is considered capable of healing properly. However, it takes longer to recover from meniscal repair surgery (normally several months) compared to meniscal resection where the recovery time is only a couple of weeks.

Degenerative meniscus tears in middle-aged people

Degenerative meniscus tears are often seen in middle-aged people and are a lot more common than traumatic meniscus tears. The meniscus tends to become fragile with age, making it susceptible to damage even without suffering acute trauma to the knee. We still don’t know enough about degenerative meniscus tears, but research is underway to learn more about them. However, they seem to occur due to aging and/or pathological changes in the knee joint that happen over a long period of time.

About one in three people over the age of 50 have a torn meniscus, but the vast majority of these experience no symptoms and thereby have little clue that their meniscus is in fact damaged. Degenerative meniscus tears seldom require surgery, and knee pain is usually caused by something else which can be treated just as well with physiotherapy. Research has proved that placebo surgery is just as effective as “real” surgery. As degenerative meniscus tears are relatively often found in conjunction with early-stage OA of the knee, rehabilitation and exercise should always be recommended as first-line treatment for knee symptoms that signalize OA.

Meniscus surgery increases the risk of knee OA

About 50% of all individuals with a torn meniscus who have undergone meniscus surgery to remove part of or the whole meniscus (meniscal resection), develop OA after 15-20 years. They are about 3-7 times more likely to develop knee OA than individuals who have a healthy knee with undamaged menisci. This increased risk of developing OA is mainly due to whether the damage was traumatic or degenerative, and if other risk factors are present. Even those who have not undergone meniscal resection are at increased risk of developing knee OA, as an injured meniscus negatively affects its primary functions. It is still not clear whether meniscus repair surgery reduces the risk of OA, but hopefully, this is the case even if a slightly increased risk of developing the joint disease most likely prevails.