Meniscus Tear Causes and Symptoms
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 during sports and many other active pursuits. This could happen whenever 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” for the femur to sit in. 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 between the thigh and lower leg and attached to the top of the tibia (leg bone) narrowing to a single, thin, detached shelf toward the center. The most important function of these discs is dispersing weight, followed closely by shock absorption and friction reduction. 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 while we engage in various activities.
- Medial meniscus – 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. Absorbs as much as half of the 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% of the weight and impact to the outer compartment of the knee.
Types of Meniscus Tear
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.
Causes of Meniscus Tear
There are many different possible meniscus tear causes, but in most cases the injury occurs when a person twists their body quickly with the knee bent while at least one foot is still planted on the ground.
Here are a few of the common meniscus tear causes:
- Age (a meniscus is worn down as one ages)
- Contact sports (e.g., football, soccer, hockey, rugby)
- Competitive sports (running, snowboarding, etc.)
- 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 will experience in their lifetime. 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.
Symptoms of Meniscus Tear
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)
Since meniscus tear symptoms can often appear similar to other injuries and conditions, it’s always necessary to have an orthopaedic surgeon make a diagnosis. An assessment, including physical examinations and diagnostic procedures such as 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 exercise, and arthroscopic surgery if the diagnosing physician finds it necessary.
The multidisciplinary team of orthopaedic experts at North Shore-LIJ Orthopaedic Institute's Trauma Services in New York treats meniscus tears as well as a broad range of conditions that affect the bones within the body.