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http://www.nytimes.com/2002/08/13/health/anatomy/13BROD.html

New Knees May Be in Order When Other Options Fail

By JANE E. BRODY

hen lesser measures can no longer control the pain and disability of arthritic knees, surgery to reconstruct or replace them then becomes a consideration. But only a consideration.

These are entirely elective procedures, and anyone who is a candidate for either would be wise to know in advance just what they involve, both during the surgery and for months afterward, and what limitations on athletic activities are likely afterward.

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The most common procedure is replacement of the working parts of the knee with synthetic devices of metal and plastic or ceramic materials that can withstand normal stresses on this weight-bearing joint for at least a decade. Another operation called high tibial osteotomy can sometimes be done to reconstruct an arthritic knee and delay the need for a total knee replacement by a decade or so. The latter is more often done on younger, physically active patients who are likely to long outlive a knee replacement.

In either case, the outcome of surgery is likely to be best when done by orthopedic surgeons who perform the procedures often and in hospitals that do 100 or more of them a year.

Total Knee Replacement

The knee is a hinge joint made up of bones, ligaments and tendons and supported by muscles. It could easily win a prize as a masterpiece in engineering. The knee can bend, slide, glide and rotate through a wide range of motions and in the process absorb up to seven times a person's weight. Unfortunately, it is also a very vulnerable joint that can deteriorate as a result of injury, disease and, most common, the stresses inflicted on it during the long and active lives so many of us now lead.

The most common reason for a knee replacement is osteoarthritis, the wear-and-tear disease in which the cushions of articular cartilage at the ends of the thigh bone, or femur, and the lower leg bone, or tibia, deteriorate, resulting in bones that rub together painfully with every step. Although most arthritic knees result from aging, an increasing number of cases occur in younger people who sustain athletic or accidental knee injuries years earlier.

Total knee replacement is a major operation most often done on people with arthritis that causes severe pain, a significant loss of mobility and an inability to perform reasonable routine and recreational activities. More than 200,000 knee replacements are performed annually in this country, most in people over 65.

In the right hands and with proper rehabilitation, it is a highly successful procedure, resulting in a pain-free knee that lasts 10 years in 90 percent of cases and 20 years in 80 percent of cases. At the Hospital for Special Surgery in New York, a ceramic knee replacement that researchers believe could last up to 25 years is being used in some patients in their early 50's or younger. Many developed severe arthritis after athletic knee injuries in their teens, 20's or 30's. The survival time of a replaced knee obviously depends on how much stress is placed on it; the more active the person, the shorter the knee's life span is likely to be.

The surgery, which typically takes two to three hours, involves cutting away the diseased parts of the joint so the replacement parts will fit precisely against the femur and the tibia. These parts are either cemented in place or made with lots of little holes into which the bones grow to hold the knee in place.

If cemented, the new joint is immediately stable, though the cement can loosen with time. The prosthetic components fit together to allow the knee to bend and to have some of the rotational movement of a normal knee. Ligaments, tendons and muscles are not involved in the surgical procedure, although misaligned leg bones and tight ligaments can be corrected. If necessary, both knees can be replaced at the same time.

The surgery risks include infection, bleeding, nerve damage and blood clots in the leg (which can be fatal if one travels to the lungs). Precautions, like donation of the patient's blood before the surgery, use of leg massager and administration of blood thinner, minimize these risks. The hospital stay is generally three to five days, and physical rehabilitation should begin during the hospital stay.

A patient goes home with crutches or a walker to be used for four to six weeks. After that, a cane can be used to help with navigation until it's no longer needed. Driving is usually resumed after six weeks, possibly sooner if the car is an automatic and surgery was performed only on the left leg.

Though many patients feel better right after surgery, several months of physical therapy to strengthen muscles and other soft tissues that support the knee are critical. The exercises can later be done on one's own and are best continued indefinitely for maximum benefit.

Full recovery from knee replacement surgery typically takes three months. Most people are then able to resume activities like bicycling, walking, swimming and golf. An active life is encouraged. But activities that involving jarring motions or quick starts and stops, like jogging, singles tennis, soccer, volleyball and basketball, should be avoided because they can damage or loosen an artificial knee.

As a precaution against serious infection, people with artificial joints are advised to take antibiotics before dental and medical procedures that can let bacteria enter the bloodstream.

Tibial Osteotomy
 

The object of this procedure is to realign a deformed knee and shift some of the excess stress on the arthritic part of the knee to the healthier part. It is typically a stopgap measure to postpone the need for knee replacement surgery for up to a decade.

The procedure is often recommended for younger patients who have arthritis in one part of the knee, either the medial (inside) half or the lateral (outside) half, resulting in bowed legs or knock-knees, respectively, and increasing the wear and pain on one side more than the other.

The surgeon cuts out a wedge of bone from the tibia to correct the deformity in the knee and realigns the bones, reallocating the space between the femur and tibia so that bone does not rub against bone on either side of the joint. The edges of the cut bone are either stapled or secured with plates and screws.

The surgery heals like a fracture, which requires up to six months for recovery. Typical hospital time is three to six days. The knee must be immobilized with a cast or brace for six weeks or longer, while the patient uses crutches. At this point, gradual weight-bearing begins, with activity increased after three months or so. As with total knee replacement, physical therapy for months is critical to a full recovery.

Anyone considering this procedure should discuss fully with the surgeon the extent of the recovery period and the limitations that will follow. Many patients regain normal knee function for routine activities, but they may not be able to resume demanding activities like skiing and tennis.

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