What is a meniscus tear?
Meniscus tears are fairly common knee injuries affecting the rubbery, crescent-shaped discs that provide cushioning between the knee bones. The meniscus is an important component of the knee; it offers shock absorption and contributes to the stability of the knee. A meniscus tear can keep the knee from functioning properly and greatly disrupt everyday life until it’s healed.
Meniscus tears often happen when people make rotating movements while their knees are bearing weight, usually during sports and other active pursuits. This could happen when someone twists the upper part of their leg as their foot and lower leg stay locked in another position. The injury can range from a minor tear, in which the meniscus stays intact, to a major split in the meniscus.
Anatomy of the meniscus
The meniscus is a C-shaped disc made of rubbery fibrocartilage that partially divides a cavity of the knee joint and provides a “cup” in which the femur can sit. Similar structures are also found at the top of the shoulder in the acromioclavicular joint, in the temporomandibular joints of the jaw, and in the sternoclavicular articulation (a synovial double-plane joint between the end of the clavicle and the first rib). In most cases, however, the term “meniscus” is referring to the discs found in the knee.
Knee joint menisci consist of two cartilaginous pads that sit between the thigh and lower leg. The two knee menisci are referred to as the medial meniscus and the lateral meniscus, which both bear the load of the body to differing degrees as we engage in various activities:
- Medial meniscus—The elongated, crescent-shaped wedge at the inner knee, which is more often injured due to the unyielding bond with the joint capsule and medial collateral ligament. It absorbs as much as half of the body’s weight and impact to the inner compartment of the knee.
- Lateral meniscus—A more flexible, mobile, circular disc at the outer knee, which is less frequently injured due to its detached nature. This meniscus absorbs as much as 80 percent of the body’s weight and impact to the outer compartment of the knee.
The meniscus is attached to the top of the tibia (leg bone) and narrows to a single, thin, detached shelf toward the center of the bone. The most important function of these discs is dispersing weight, followed closely by shock absorption and friction reduction.
Types of meniscus tears
There are several ways of classifying meniscus tears, such as by the location, the specific tear pattern or proximity to the blood supply. The tears may be located in the inner, outer or middle third of the meniscus, with tears in the outer third having the best chance of healing, due to better blood supply.
Tears may be located in the following areas of a meniscus disc:
- Anterior horn
- Posterior horn (most common tear location)
These are the most common tear patterns that occur in meniscus injuries:
- Degenerative, complex tears (more than one pattern)
- “Bucket handle” tear patterns
- Flap tears (displaced flap)
- Horizontal “cleavage” tears
- Longitudinal, peripheral tears
- “Parrot beak” tear patterns
- Radial tear patterns
These are a few of the factors that decide whether a tear to the meniscus can be repaired:
- Activity level
- Length of the tear
- Location on the meniscus
- Tear pattern
- Whether the patient has other related injuries
Depending on the tear’s proximity to the blood supply, meniscus tears may be classified as white-white, red-white, or red-red. The red-red area has the best blood supply and hence the best chance to heal. Unstable tears can move and cause problems during the healing process, whereas stable tears can sometimes heal on their own.
Everyone experiences these injuries differently and only medical professionals are qualified to make a diagnosis, but the following are the most common meniscus tear symptoms:
- Clicking in the knee
- Locked knee joint
- Pain in the knee (particularly when holding it in a straight line)
There are many different reasons for meniscus tears, but in most cases the injury occurs when a person twists the body quickly, with the knee bent, while at least one foot is still planted on the ground.
Here are a few of the common causes of meniscus tears:
- Age (a meniscus is worn down as one ages)
- Contact sports (e.g., football, soccer, hockey, rugby)
- Competitive sports (running, snowboarding)
- Heavy lifting/bending
Forceful twisting of a weight-bearing leg while the knee is bent often leads to an acute tear, which approximately 61 out of every 100,000 people experience. Degenerative tears, on the other hand, are more common in people over the age of 65, after the meniscus has become weaker and less elastic. Even minor accidents can lead to a degenerative meniscus tear in an older person.
Since meniscus tear symptoms can often appear similar to other injuries and conditions, it’s always necessary to have an orthopedic surgeon make a diagnosis. An assessment, including physical examinations and diagnostic procedures such as an X-ray and MRI, can help doctors determine the best treatment plan based on age, extent of injury, overall health, medical history and other factors. There are non-surgical treatments such as icing, medication and muscle-strengthening exercises. Arthroscopic surgery is also an option if the diagnosing physician finds it necessary.