Figure 1: Right Knee - Anterior View with Patella Tendon Removed

Medically speaking, the "cartilage" is actually known as the meniscus. The meniscus is a C-shaped piece of fibrocartilage which is located at the peripheral aspect of the joint. The majority of the meniscus has no blood supply. For that reason, when damaged, the meniscus is unable to undergo the normal healing process that occurs in most of the rest of the body. In addition, with age, the meniscus begins to deteriorate, often developing degenerative tears. Typically, when the meniscus is damaged, the torn piece begins to move in an abnormal fashion inside the joint.


Figure 2: Meniscal Tear with Fragment: MR is the intact meniscal rim. MF is the torn meniscal fragment.
Because the space between the bones of the joint is very small, as the abnormally mobile piece of meniscal tissue (meniscal fragment) moves, it may become caught between the bones of the joint (femur and tibia). When this happens, the knee becomes painful, swollen, and difficult to move.


Figure 3: Torn medial meniscus with fragment located at peripheral aspect of joint.
Figure 4: Torn meniscal fragment dislocated into knee joint.


The meniscus has several functions:

As secondary stabilizers, the intact meniscii interact with the stabilizing function of the ligaments and are most effective when the surrounding ligaments are intact.

The meniscii act as spacers between the femur and the tibia. By doing so, they prevent friction between these two bones and allow for the diffusion of the normal joint fluid and its nutrients into the tissue which covers the end of the bone. This tissue is known as articular cartilage. Maintenance of the integrity of the articular cartilage is critical to preventing the development of post-traumatic or degenerative arthritis.

The biconcave C-shaped pieces of tissue known as meniscii (cartilage in non-medical terms) lower the stress applied to the articular cartilage, and thereby have a role in preventing the development of degenerative arthritis.


When a physician is evaluating an injured knee, a history is taken to determine the specific problems that a patient is having with the knee. Next a physical examination of the area will be performed to determine the site of the pain, the presence or absence of physical findings that are known to be associated with a torn meniscus, and x-rays are performed to identify other abnormalities that may give similiar problems to those of a torn meniscus. In some instances, additional diagnostic tests such as an MRI may be ordered. If the history and physical findings indicate that a tear is present, arthroscopic surgery may be indicated for treatment.

Figure 5: Side view of knee. Circled area contains an area of normal meniscus.
Figure 6: Side view of knee. Circled area contains an image of a portion of the meniscus. The light center area represents the tear.
Figure 7: Side view of knee. Circled area contains an image of a portion of the meniscus. The red area is a color enhanced tear of the meniscus.

The most commonly performed surgical procedures on the knee include a meniscectomy (removal of the meniscus), meniscal repair, and ligament reconstruction. The traditional method of surgery for a torn meniscus (cartilage) involves admission to a hospital for several days, one or more surgical incisions that may average several inches, several weeks on crutches, and up to several months to completely rehabilitate the knee. This is called an arthrotomy in medical terms.

The arthrotomy method of doing surgery has been gradually replaced by a procedure known as arthroscopy. This is still a surgical procedure, but with several differences. Arthroscopy involves inserting a fiberoptic telescope that is about the size of a pencil into the joint through an incision that is approximately 1/8 inch long. Fluid is then inserted into the joint to distend the joint and to allow for the visualization of the structures within that joint. Then, using miniature instruments which may be as small as 1/10 of an inch, the structures are examined and the surgery is performed.


Figure 8: Drawing of Meniscal Tear with Fragment Removal.

This is usually done as an outpatient. On the average, most patients are able to walk without crutches within 48 hours. An active rehabilitation program is then initiated in an effort to rebuild the muscle strength in the muscles around the knee, thus relieving the stress on the knee. In most patients, an exercise program is started by the seventh post-operative day on Nautilus type equipment. Patients are usually on some type of activity restriction for approximately 6 weeks after surgery, or until rehabilitation has been successfully completed. Obviously these general guidelines must be individualized and may change during the recovery phase. Arthroscopy is much less traumatic to the muscles, ligaments and the tissues than the traditional method of opening the knee.

Occasionally, it is possible to repair a torn meniscus. While this may be done arthroscopically, because of the slow healing process of the meniscus, the recovery time is longer then simply removing the torn piece of meniscus (meniscectomy). Unfortunately, as a person gets older, the possibility of the tear being repairable greatly decreases.



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