Articular Cartilage
Kevin G. Shea, M.D.The thigh bone and shin bone meet at the knee joint. The ends of these bones are covered with smooth articular cartilage. This surface resembles a pearl, i.e. a smooth, polished, white, glistening surface. This surface has a lower coefficient of friction than any man-made substance. This allows for the smooth motion of the knee, in terms of bending and straightening the knee. The inner surface of the knee cap (patella) is also covered with articular cartilage.
INJURIES TO THE ARTICULAR CARTILAGE
The articular cartilage can be injured in several different ways. Twisting injuries or direct blows to the knee can damage this tissue. Articular cartilage is frequently injured during ACL (Anterior Cruciate Ligament) tears or meniscal tears. The healing potential of articular cartilage is limited, and many of these injuries can lead to future problems with the knee, such as arthritis. There are several surgical procedures designed to promote healing of articular cartilage injuries.
SURGERY TO REPAIR DAMAGE TO THE ARTICULAR CARTILAGE
Articular cartilage damage can lead to recurrent symptoms, such as swelling or fluid in the knee, catching, popping, locking, giving out, etc. Once a significant injury to the articular cartilage has occurred, this tissue has limited potential for healing. In many cases, surgery will be required to promote healing. Several surgical options exist, and your surgeon will determine the best option in your case. Options include:
ABRASION CHONDROPLASTY OR SUBCHONDRAL BONE MICRO-FRACTURE:
The damaged cartilage flaps are removed. The bone surface underneath the cartilage will be treated by placing a series of small holes or 'micro-fractures' into the bone. This process promotes healing, by producing a 'scar cartilage', to fill the gap left by the damaged cartilage.
CARTILAGE TRANSPLANTATION: In some cases, cartilage transplantation may be necessary. In cases where the abrasion chondroplasty technique does not produce acceptable results, transplantation of articular cartilage may be necessary. This may require cartilage from a cadaver, or even use of the patients own cartilage. Cartilage from one region of the knee can be transferred to another region of the knee.
In some cases, cartilage transplantation may consist of removing a portion of cartilage. This cartilage will be sent to a lab, grown into more cartilage tissue, and then transplanted back into your knee. A second operation is required to transplant the new cartilage tissue.
OSTEOTOMY. In some cases, the knee may require a procedure to change the overall alignment of the knee joint. This will transfer pressure away from injured cartilage. This procedure places a cut in the bone and either wedges the bone open or closed. This procedure is designed to change the alignment of the thigh bone or the shin bone.
Damage to the articular cartilage can be very frustrating for patients, because the articular cartilage has limited potential for healing. Although surgical treatment of cartilage injuries can improve the function of the knee, it can be difficult to make the knee as well as it was prior to the injury. At this stage in surgical technology, these procedures are designed to improve knee function as much as possible. In some cases, we may limit your knee motion in a brace, require crutches, or prohibit weight bearing on your limb for 6-8 weeks after surgery. Any attempt at surgical repair requires that the cartilage be protected during the post-operative period, to allow for more complete healing of your injured cartilage.
Your commitment to a post-operative rehabilitation program is crucial, and compliance with motion or weight bearing restrictions is very important. For cartilage repair surgery, you will require extensive post-operative therapy. In many cases, a physical therapist will help you with your rehabilitation, and design a program for rapid recovery. You will need to be an active participant in exercises to regain motion, decrease swelling, recover strength, and fully recover from your surgery. In many cases, the use of an exercise bike will be very helpful for your rehab. We recommend that you borrow or purchase an exercise bike, or join a gym that allows access to exercise equipment.