Meniscal Tears and Osteoarthritis

Meniscal tears are common knee injuries. Most often, you hear about athletes who experience meniscal tears, but actually, any individual at any age can tear a meniscus.

Three bones come together to form your knee joint—the femur (thighbone), tibia (shinbone), and patella (kneecap). Between the femoral and tibial components of the knee, there are two wedge-shaped pieces of cartilage—each one is called a meniscus. Each tough and rubbery meniscus serves to cushion the knee joint and stabilize it.

A meniscus can tear. Often, a meniscal tear occurs suddenly during athletic activity. Contact sports (for example, football) can easily cause a meniscal tear—but you can squat or twist the knee and cause a meniscal tear, too. In older people, meniscal tears can occur after cartilage wears thin and weakens. If the menisci are weakened due to aging, any sort of twisting movement can be enough to cause a tear.

There are different types of meniscal tears: bucket handle, transverse, longitudinal, flap, parrot-beak, and torn horn. The name is based on where the tear occurred on the meniscus.

The first sign of a meniscal tear may be that you feel a "pop" in the knee. Other symptoms commonly associated with a meniscal tear include pain, stiffness, swelling, locking knee, the feeling of your knee giving way, and restricted range of motion. A piece of torn meniscus can detach and become loose, potentially causing your knee to pop, slip, or lock.

An MRI can help detect a meniscal tear. X-rays do not show meniscal tears as they are in cartilage rather than in bone. Doctors can also utilize a McMurray test to help diagnose a meniscal tear. With the McMurray test, your doctor will bend and straighten your knee while gently twisting your shin bone. Feeling or even hearing a click along the sides of your knee suggest a torn meniscus.

Treatment of a meniscal tear depends on several factors, including the location of the tear, your age, and your activity level. The outer third of the meniscus has more blood supply than the inner two-thirds. A tear on the outer, more vascularized part of the meniscus may heal on its own or it can be repaired using arthroscopic surgery. A tear on the inner, less vascularized part of the meniscus is usually trimmed away since the margins of the tear often cannot grow back together. Rehabilitation usually follows a post-surgical period of knee immobilization. If the approach to healing is non-surgical, rest, ice, compression, and elevation (R.I.C.E.) are important.

According to a study published in 2012 there are more than 300,000 knee arthroscopies performed each year in the United States on patients who have a meniscal tear and osteoarthritis in the same knee compartment—as if surgeons might be able to fix both problems at once. While arthroscopy is considered effective for meniscal tears alone, its effectiveness for associated osteoarthritis is less clear. There is strong evidence that arthroscopy is not beneficial for knee osteoarthritis alone, thus the American Academy of Orthopedic Surgeons cannot recommend this therapy for knee osteoarthritis.

The MeTeOR study (Meniscal Tear With Osteoarthritis Research), was conducted to evaluate the effect of arthroscopy versus non-surgical treatment in a group of more than 300 patients with both a meniscal tear and mild to moderate knee osteoarthritis. Seven orthopedic centers in the United States werre involved in the study, which was sponsored by the National Institutes of Health. It concluded that there were no significant differences in functional improvement between the surgical and non-surgical groups. However, a third of the patients that had physical therapy alone underwent surgery within six months.

Several studies have concluded that a meniscal tear can lead to knee osteoarthritis.  On the flip side of that, knee osteoarthritis can lead to a spontaneous meniscal tear through breakdown and weakening (degeneration) of the meniscus. A degenerative meniscal lesion observed on MRI is suggestive of early osteoarthritis. Even with surgical resection to remove degenerative lesions, osteoarthritis may still progress.

Partial meniscal resection has been associated with less radiographic knee osteoarthritis (i.e., knee osteoarthritis observed on x-ray) than total meniscectomy. There is also evidence that meniscal damage not treated surgically remains a significant risk factor for the development of radiographic knee osteoarthritis.