Meniscus Tear in the Knee
The meniscus is a quarter moon-shaped structure made from fibrocartilage that partially divides the joints in the knees, acromioclavicular joints, sternoclavicular joint and the temporomandibular joint. The knee joint menisci are the ones to be discussed in this article. In the knee, there are the medial and lateral menisci. The medial meniscus is the one more injured. Both help the knee to stay stable when torsion or tension is placed on the joint.
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The knee menisci look like cartilaginous pads that spread the friction around the knee joint. They are flat on the bottom and concave across the top. They are attached to the knee joint by their attachment to small depressions between the intercondyloid fossae of the tibia. They also disperse the weight of the rest of the body on the joint.What are Meniscus Tears?The menisci are made of cartilage and form the “articular cartilage” that makes up part of the joint. A “cartilage” tear in the knee is the same thing as a meniscus tear. The most common cause of a cartilage tear in the knee is trauma, such as is seen in a motor vehicle accident or a sports injury. This is called a traumatic tear. A degenerative tear happens when older people have degeneration of the menisci over time. The cartilage is more brittle and tears more easily.Meniscus tears usually occur along with damage to the anterior cruciate ligament and the medial collateral ligament. Athletes refer to this injury as the “unhappy triad” because it sets the athlete back in a serious way. The actual injury is caused by turning quickly or twisting the knee, often when the knee is bent and the foot is planted.Symptoms of a Meniscus TearThe main symptom of meniscus tears includes pain and swelling in the affected knee. Often the injured knee feels like it’s locking or that it won’t straighten up. This happens when the cartilage physically impinges on the joint of the knee.Common symptoms of a meniscus tear include:
- Pain in the Knee
- Knee swelling
- Tenderness to palpation of the meniscus
- Locking, popping or clicking within the joint
- Limitations in the motion of the knee
- Minor tear: This results in swelling and slight pain. The symptoms usually resolve in about 3 weeks.
- Moderate tear: There is pain in the middle or side of the knee. Swelling worsens after 2-3 days. The knee will feel stiff and you won’t be able to bend it completely. There will be sharp pains with twisting the knee or when you squat down. Symptoms last about 1-2 weeks but will recur for years if you don’t have the tear treated surgically.
- Severe tear: There are pieces of the meniscus floating free in the joint space. This is why the knee pops, catches or locks. Straightening the knee may not be possible.
Causes of Meniscus TearsThe menisci are made of tough fibrocartilage, which makes them stronger and resistant to injury than regular cartilage. The medial meniscus sits on the medial tibial plateau; the lateral meniscus rests on the lateral tibial plateau.
The menisci have tiny vessels nourishing the outside of their surface. In the middle of the menisci, however, there is no actual blood supply so when the fibrocartilage gets injured, it has little vasculature to allow it to heal.
The two main causes of a meniscus tear include a traumatic injury that occurs when the knee is bent and then twisted. A hit on the outside of the knee causes a medial meniscal tear plus an injury to the medial collateral ligament and the anterior cruciate ligament. Traumatic injuries usually occur in people who are active and are between the ages of 10 years and 45 years. Most of these injuries require a surgical repair.
Degenerative tears are more common in those people over the age of 40. They happen when the collagen fibers break down as a result of wear and tear. These types of tears are generally horizontal and result in segments that generally don’t catch or lock the knee. They are more common in smokers and interfere with stair climbing and getting out of cars and chairs.Diagnosis of Meniscus TearsAn orthopedist can palpate the joint for tenderness along the joint line and get a complete history of what happened to the patient. There are a number of tests a doctor can do to evaluate the stability of the menisci. The following are some of the best tests:
- The McMurray Test: The patient lies back with the knee and hip flexed. The foot is rotated externally as the knee is extended with a medial force placed on the knee. The idea is to reproduce a snapping sensation. It puts pressure on the medial meniscus at the level of the medial femoral condyle.
- The Fouche’s sign: The doctor holds the tibia rotated internally. This stresses the medial meniscus. The tibia starts out extended and is slowly flexed, catching the meniscus between the femur and tibia for a time before it abruptly slips posteriorly, leading to a snapping sound and pain.
- The Steinmann I Sign. The knee is almost all the way extended and the examiner sharply rotates the tibia in the internal or external rotation while the knee is slowly flexed. It will show pain if there is a meniscus tear. Lateral rotation of the tibia puts stress on the medial meniscus, while medial rotation stresses the lateral meniscus.
- The Steinmann II Sign: Palpate the sore meniscus in the joint line. Slowly flex the knee. If the part of the joint loses its tenderness, it likely involves a torn meniscus. If the tenderness persists during flexion, the problem is likely a collateral ligament tear.
Surgical therapy can be used if conservative therapy fails or if the knee locks. Repair is possible to the outer one-third of the meniscus because an adequate blood supply is in place for adequate healing. Younger patients are better suited to surgery than older patients. People who are sedentary usually don’t have a good outcome.
Toward the inside of the knee, the meniscus has no blood supply and it is not likely that it will heal. In such cases, the patient will have arthroscopy and undergo a partial meniscectomy. In serious cases, the patient needs a total meniscectomy, although doctors avoid this whenever possible. The loss of the entire meniscus usually leads to osteoarthritis of the knee which, in turn, leads to a total knee replacement or possibly a meniscus replacement. An experimental approach is called a “meniscus transplant”. It is not very commonly done as yet.
After surgery, the patient needs to have a rehabilitation program. The rehab done depends on whether the entire meniscus was removed or not. While in rehabilitation, some people successfully take glucosamine-sulfate. If the destroyed part of the meniscus was removed, patients can begin using a crutch within two days of surgery.
They can return to regular activities within three weeks. Walking normally, however, often takes up to 3 months. Most patients with meniscus removal will never feel completely back to normal again.
If the meniscus was actually repaired, the rehabilitation is generally very extensive. A hinged brace is placed on the patient and the patient is made to walk the first day after surgery, using crutches. Partial weight bearing is allowed right after surgery. The goal of rehabilitation is to restore function and improve symptoms, as well as the prevention of subsequent injuries. The culmination of rehabilitation is the restoration of range of motion, muscle function, and leg coordination. Rehabilitation is tailored to the patient and to the type of injury they had.Epidemiology of Meniscus TearsA tear of the meniscus is the most common injury to the knee. It is a frequent injury in soccer and football. The injury is more common with males at a ratio of 2.5 to 1. Males who are between the ages of 31 and 40 have an increased chance of a meniscal tear. Females tend to tear their meniscus between the ages of 11 and 20. Those with a greater BMI have a higher risk of meniscal tears. The average length of stay for patients who are hospitalized for repair of their meniscal tear is about 3.1 days.Complications of a Meniscus TearThe meniscus is important. If you suffer a meniscus tear, there are certain complications you might expect:
- Wearing out of the cartilage associated with osteoarthritis
- The meniscus can flip over resulting in a clicking sensation in the knee when bent
- The knee can lock
- There can be ongoing knee pain
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Editor’s Note: This page has been updated for accuracy and relevancy [cha 6.5.19]