Q: I’m 55 and have a bad right knee from playing lots of sports. I’m interested in getting a partial knee replacement. I’ve heard the recovery is shorter and the result is better than a total replacement. What do you think?
A:
The first decision you and your orthopedic surgeon need to make is whether you need an operation. Joint replacement works to relieve pain and will help the knee function better. If your knee pain prevents you from performing daily activities — walking climbing stairs light yard work — a replacement should be considered.
But a lot of flags go up if you are thinking that a replacement will let you return to playing vigorous sports. No knee replacement whether full or partial should be subjected to impact loading — the pounding that occurs when you run or jump. The replacement joint will loosen up and parts of it will wear out faster so it will almost certainly not last as long. Knee replacements really aren’t the answer for people with arthritic knees who want to go back to the days when they could run for miles or play a hard game of pick-up basketball.
The term “knee replacement” may conjure notions that the entire joint is replaced. In fact the operation might best be thought of as a major resurfacing that replaces cartilage which in a healthy knee allows the femur (thighbone) patella (kneecap) and tibia (shinbone) to move smoothly against one another without pain.
In a total knee replacement the portions of the femur and tibia that meet to form the joint are cut away and covered with prostheses to restore smooth movement. In a partial replacement used when arthritic degeneration of the cartilage is more localized smaller parts of the femur and tibia are cut away and resurfaced.
As you noted the recovery from a partial replacement is shorter and range of motion afterward is better. But there’s a lot of controversy about who should get one. They aren’t well-suited for people with very bowed or knocked knees. And they’re a good choice only if the knee still contains a fair amount of healthy cartilage.
For someone your age one important thing to think about is how long a knee replacement will last. Most studies show that total knee replacements last longer than partials because the components that attach the prostheses to the bone are less likely to loosen up. Another problem: T he cartilage that wasn’t replaced initially because it was in good shape may become diseased and arthritic later on so people end up with the knee pain that the replacement was supposed to get rid of.
It’s true that when a replacement fails you can have it redone — a procedure orthopedic surgeons call a revision. Of course there are many reasons you’d want to avoid a revision; it’s major surgery after all. But one big drawback is that the second set of prostheses usually won’t last as long as the first. When the first set loosens up the bone tissue gets damaged so the new set often can’t be anchored quite as securely to the bone. As a result a revision doesn’t last as long and may not provide as much pain relief as the initial replacement.
Dr. Donald T. Reilly, Harvard Health Letter Editorial Board, New England Baptist Hospital, Boston.
