WHAT IS THE MENISCUS?
The menisci are semicircular, "C-shaped" cartilages in the knee. Each knee has an inner medial meniscus and an outer lateral meniscus. These cartilage "bumpers" serve several functions:

• shock absorption between the two sides of the knee
• lubrication of the knee surfaces
• increasing surface area of contact between the knee surfaces
• enhancing knee stability

WHAT HAPPENS WHEN THE MENISCUS IS DAMAGED?
Injuries to the knee can result in tears, destruction, or loss of the meniscus. Often, these problems can be addressed by partially removing torn or damaged fragments or by repairing tears through the arthroscope. However, in some cases the meniscus can be irreparably damaged, and must be removed completely. While complete removal of the meniscus, or total meniscectomy will resolve the pain, clicking, and locking of the knee associated with torn fragments, the complete loss of the important functions of the meniscus will result in early joint degeneration, or arthritis within the knee. Over time, the knee can become extremely painful as normal knee function is impaired.

DOES THE MENSICUS ALWAYS NEED TO BE REPLACED?
No. Depending on the age and demands of a person, the meniscus-deficient knee may function acceptably for a time. In persons who already have a significant degree of arthritis or joint destruction (found by X-ray or at arthroscopy), a meniscus replacement will not function optimally. The worn knee can actually tear up the replaced meniscus. In such cases, it is probably best to wait and see if the knee becomes painful and function is impaired. At that time, other alternatives are available.

However, in younger patients with little evidence of joint disease, studies have shown that meniscal replacement can offer predictable pain relief and improved knee function. Animal studies indicate that early meniscal replacement in the meniscus-deficient knee can slow the progress of osteoarthritis as well.

HOW IS THE MENISCUS REPLACED?
Since 1984, orthopaedic surgeons have attempted to relieve pain and halt the progression of arthritis in the meniscus-deficient knee by replacing a donor meniscus into the affected joint. To date, thousands of these procedures have been performed worldwide.

The process begins with the selection of an appropriately sized, cryopreserved "donor" meniscus, or allograft. Despite the popular concerns over tissue donation, allograft meniscal tissues have rarely been a source of disease transmission or "rejection", and such menisci are scrupulously obtained and screened for problems. The meticulous process of sterilization and refrigeration (called "cryopreservation") is performed by reputable companies that adhere to strict standards.

Using arthroscopic techniques and very small incisions, the allograft is inserted into the recipient's knee and fixed in place. Over time, the body uses the meniscal allograft as a "scaffold" or "mold" and the tissue is eventually "repopulated" with cells and tissues from the recipient. After a rehabilitation period of a few months, the patient can resume his or her usual activities.

WHEN SHOULD SURGERY BE PERFORMED?
The decision to undergo meniscal transplantation should be made with the help of your orthopaedic surgeon. A knee with no meniscus can function relatively well for a time, but damage to the surrounding joint surfaces is inevitable. Because the results of meniscal transplantation are less predictable in the damaged knee, the decision to transplant is usually made when the knee first starts to become painful, but before significant cartilage destruction has occurred. Oftentimes, frequent bi-annual knee checks and occasionally a diagnostic arthroscopy (using the arthroscope to evaluate the knee) will help the patient and physician make the decision as to when the procedure should be performed.