Meniscus (anatomy)

This article is about the parts in the human knee.
For other uses of the term meniscus, see meniscus and lens (optics).

In anatomy, a meniscus is either of two specific parts of cartilage of the knee. The knee contains a lateral meniscus and a medial meniscus. Both are cartilaginous tissues that provide structural integrity to the knee when it undergoes tension and torsion. The menisci are also known as 'semi-lunar' cartilages - referring to their half-moon "C" shape - a term which has been largely dropped by the medical profession, but which led to the menisci being called knee 'cartilages' by the lay public.

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Anatomy

    The menisci are two pads of cartilaginous tissue which serve to disperse friction in the knee joint between the lower leg (tibia) and the thigh (femur). They are shaped concave on the top and flat on the bottom, articulating the tibia. They are attached to the small depressions (fossae) between the condyles of the tibia (intercondyloid fossa), and towards the center they are unattached and their shape narrows to a thin shelf.^[1]

Function

The menisci act to disperse the weight of the body and reduce friction during movement. Since the condyles of the femur and tibia meet at one point (which changes during flexion and extension), the menisci spread the load of the body's weight.^[2] This differs from sesamoid bones, which are made of osseous tissue and whose function primarily is to protect the nearby tendon and to increase its mechanical effect.

Injury and surgical options

Tears

In osteoarthritis, the meniscus is either torn or worn away from overuse, age, or injury. The joint will be in pain when in use, but when there is no load, the pain goes away. A torn meniscus can be repaired through some surgery and the body's ability to heal itself. In addition, there are techniques under research which involve sutures and biological glues to enable healing. If the tear is far away from the meniscus' blood supply (the meniscus becomes avascular towards the unattached, thin interior edge), then repair is unlikely. In these cases arthroscopic surgery allows for a meniscectomy, removing the torn tissue and allowing the knee to function with some of the meniscus missing. Usually younger patients are more resilient and react well to this treatment, while older, more sedentary patients do not have such rejuvenating ability. In situations where the meniscus is torn beyond repair or partial removal, a total menisectomy and meniscus replacement may be the only option before a total knee replacement.

In sports and orthopedics, people will sometimes speak of "meniscus surgery" and a "torn meniscus" and be referring to an injury to one of the menisci. Tears in the meniscus may be assessed and measured via a minimally invasive test called meniscometry.

Meniscus Treatment

When a person tears their meniscus they should consult a doctor. After having the proper medical examinations an orthopedist will decide if the patient should have surgery or not. In the case that the doctor decides that surgery is not necessary, the patient will probably have to take a small break from his or her normal activities, allowing the knee to heal. A victim of a torn meniscus should try strengthening exercises for the knee muscle (stronger and bigger muscles will protect the meniscus cartilage by absorbing a part of the weight) and may be given some anti-inflammatory medications.

Rehab after Meniscus Surgery

After a successful surgery for treating the destroyed part of the meniscus patients must follow a rehabilitation program to have the best result. The rehabilitation following a meniscus surgery depends on whether the entire meniscus was removed or repaired.

If the destroyed part of the meniscus was removed, patients can usually start walking a day or two after surgery and return normal activities after a few weeks (2 or 3). However, each case is different and patients must consult the surgeon.

If the meniscus was repaired the rehabilitation program that follows is a lot more intensive. After the surgery a hinged knee brace is placed on the patient. This brace allows controlled movement of the knee. The patient is encouraged to walk using crutches from the first day, and most of the times can put weight on the knee. After four weeks the patient can start walking using the hinged knee brace only. Starting from the second month the patient can walk freely and can also do various "light" exercises (static bicycle, swimming, etc.). If the rehabilitation was done properly the patient can gradually return back to "heavier" activities (like running). However each case is different and the patient must consult the doctor and physiotherapist regarding a proper rehabilitation program.

References

1. ^ Gray's Anatomy of the Human Body. 1918. 7b. The Knee-joint.  
2. ^ About.com's orthopedics section, by Jonathan Cluett, M.D.

See also

• Meniscal cartilage replacement therapy
• Unhappy Triad– a set of commonly co-occurring knee injuries which includes injury to the medial meniscus