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Published on October 20, 2020

When is it time for knee replacement surgery?

Knee Replacement Surgery

Knee replacement procedures are very common in older adults. The American Academy of Orthopaedic Surgeons estimates that about 790,000 Americans have total knee replacement surgery each year. It is usually a very successful surgery that allows people to resume favorite activities, such as walking or golfing, with a lot less pain.

The timing for knee replacement surgery is important, but a recent study shows that some patients may not be getting their surgery at the optimum time. The research, done by a team at Northwestern University’s Feinberg School of Medicine in Chicago, found that many get the surgery either too early or too late. 

The study of 8,002 people over the course of eight years found that 90 percent of the patients who could benefit from knee surgery waited too long and 25 percent of the patients had the surgery too soon. Researchers say that neither option is optimal.

Patients who wait too long “needlessly suffer,” said Orthopedic Surgeon Robert Wilsterman, MD, at Orthopedic Specialists in Falmouth. “They also risk damaging their joint, requiring more extensive surgical procedures.”

“You may get to the extreme where you’ve waited to the point where the deformity gets so bad that it can’t be corrected. You don’t have to have a bad outcome, but you certainly can wait so long that your outcome is in jeopardy,” he said.

The other side of the coin with people having knee replacement surgery too soon also has its downside, in Dr. Wilsterman’s opinion. Some patients are of the mindset that their knee is bad, and they are healthy, so they might as well get it over with. That isn’t a wise choice for several reasons, he said.

“The device does not have unlimited longevity. They wear out and they wear out faster in younger people because of the increased activity level. Also, and this is very specific to knees as opposed to hips: knees never really feel normal. They always feel different and young people don’t like that. So, people who jump the gun tend to be unhappy because they were expecting a situation where they returned to feeling the way they did when they were young.”

The biggest problem with having knee surgery too early is that it greatly increases the risk of the patient needing a revision knee surgery at a later date. While revision surgeries are much more effective and successful than they used to be, they are almost never as good as the primary surgery, Dr. Wilsterman said. How long the knee replacement lasts depend on a lot of factors, including how well the knee was placed during surgery. Obesity and how much abuse the knee gets can also affect the length of life for the replacement knee.

The average age for knee replacement surgeries is 66 years old, according to Dr. Wilsterman. Anybody younger than that at the time of their first knee replacement faces the possibility of a revision surgery.

Part of the reason that so many people have knee replacements too young is that a lot of doctors rely on X-rays to determine whether a replacement is in order. Dr. Wilsterman thinks that is a mistake. He has seen people with X-rays that show a lot of deformity, but the person is doing very well. He has also seen people in a lot of pain who have X-rays that look fine. While he does look at X-rays, he also looks for other symptoms that would justify replacing a knee.

“It’s very, very complex and it doesn’t lend itself to any kind of formula,” he said. “My standard speech is to tell people that when your knee gets to the point where it starts to dictate the terms of your life, you don’t have to live like that. We can fix it. But if you have occasional pain that is just an annoyance and you don’t mind that, good for you. You can exist like that for a long time, regardless of what your X-ray looks like.”

The most common reason people on the Cape suffer from knee pain and need joint replacement surgery is because of arthritis, which damages the cartilage of the knee. When the cartilage is sufficiently damaged, the stress of weight bearing is no longer born by the bones in the way it was intended. Once that occurs, you get what doctors call “bone on bone,” which then acts like sandpaper grinding down the bones and causing deformity, he said.

Some people with arthritis in their knees become knock-kneed and others become bow-legged. A few patients have one of each, which makes their gait very lop-sided.

Age isn’t the only risk factor for arthritis, Dr. Wilsterman said. Arthritis has a strong genetic component, but there are some lifestyle adjustments people can do to prevent damage. These include prevention of obesity and placing limitations of impact loading on the joints. Things like constantly jumping off a work truck or running marathons could exasperate the knee going downhill. A well-balanced diet so your body has all the nutrients it needs is also a good idea.

“The problem with cartilage is that it is largely inert,” he said. “It’s not really living tissue in the sense that muscle or bone is. It has a very, very limited healing potential, if any. It’s more like a piece of plastic than a living thing, so once it gets damaged there’s not much you can do to fix it. The only way to prevent it from falling apart is to prevent it from getting damaged in the first place.”