By Robert Dow Hoffman, M.D
As we all know, the knee joint is the connection of the femur (thigh bone), and the tibia (shin bone), with the patella (kneecap) located in front of the femur. The ends of these bones are covered by a smooth, slippery surface of connective tissue called articular cartilage. Only a few millimeters thick, these surfaces along with a small amount of joint fluid allow the knee joint to function painlessly in many people for many years. In addition to this articular cartilage, another important cartilage structure called a meniscus is found inside the knee. The meniscus is a wedge-shaped cushion located between the tibia and femur and helps evenly distribute the pressure between the bones. Each knee has two menisci, and they are made of a different, more fibrous type of cartilage than that found on the joint surfaces. Up until the 1970’s, the menisci were not thought to be very important for knee function. If a meniscus caused a problem in the knee, it was usually completely removed during a surgical procedure called a meniscectomy . We know now that these procedures increased the risk of developing knee arthritis later in life. The importance of preserving all of the different cartilage structures in the knee lies in the fact that they have a very limited capacity to repair themselves when injured. Also, despite all the technological advancements in medicine, cartilage remains a difficult tissue to replace when it is gone.
Knee pain and injuries are very common, and cartilage damage accounts for a large percentage of these problems. Injuries to the meniscus are often referred to as “cartilage tears.” These tears cause pain usually on either side of the knee along with swelling. Sometimes, the knee may feel like it is catching or locking when it bends and straightens. In younger patients, meniscal tears are often the result of a specific injury. In older patients, these tears often occur spontaneously as the menisci wear. Many of these injuries can be managed with rest, medication, and occasionally an injection of medication into the knee. If these simple treatments are not effective or if catching and locking occur, a small camera or arthroscope can be inserted into the knee and the torn cartilage can be removed or, less commonly, repaired. More recently, surgeons have attempted to transplant menisci from cadavers into injured knees, but the long term results of this procedure are not available.
Damage to the articular or joint surface cartilage presents a more difficult problem. These injuries, like meniscal injuries, often cause pain and swelling as well as catching sensations in the knee. Again, in young patients, these are often the result of an injury and are usually associated with other injuries in the knee such as ligament or meniscal tears. In older patients, defects in the articular cartilage are usually the result of the slow wear and tear of the joint surfaces, a process known as osteoarthritis. Small, isolated defects in the joint surface often will not impair knee function greatly. Larger defects, especially in young people can cause significant pain and disability and can be treated with a variety of surgical methods. These include: simple smoothing or debridement of the area, making small holes in the defect in an attempt to stimulate healing, transplantation of cartilage from elsewhere in the knee or from a cadaver, or the transfer of synthetic material into the defect to serve as a scaffold for joint cartilage growth. These methods often do not work as well in the setting of osteoarthritis. Most treatments for osteoarthritis are aimed at pain relief and not restoration of the joint surface. These include pain and anti-inflammatory medication, bracing, injection of steroids and/or cartilage proteins, rest, dietary supplements, etc. The most commonly performed surgical procedure to relieve the pain of an arthritic knee is the knee replacement, although this option is reserved for people who continue to have severe, disabling pain despite non surgical treatment.
Questions regarding a specific knee problem or treatment can be best answered by an orthopaedic surgeon.
For more information about this article or other orthopedic problems – contact Dr. Hoffman at Chatham Orthopaedics, 4425 Paulsen Street, Savannah, GA 31405,