For millions of Americans, knee replacements have redefined what it means to get older. People who in the past would have been incapacitated by painful arthritis can now enjoy years of active life—walking, climbing stairs, cycling, swimming, and more. Small wonder almost 1 million total knee replacements are performed annually in the United States. As baby boomers age, that number is expected to climb rapidly.
If you have osteoarthritis in one or both knees and are beginning to experience significant pain and stiffness, chances are you’re already wondering if it’s time to consider a total knee replacement, also known as total knee arthroplasty. Timing, it turns out, is critical. Wait too long, and you may suffer needless discomfort, and you may not reap the benefits of knee replacement that you would if you’d had it done earlier. Get a knee replacement too early, and the risks may outweigh the benefits.
Unfortunately, many people get the timing wrong, according to new findings by researchers from the Feinberg School of Medicine of Northwestern University, published in the Journal of Bone and Joint Surgery in January 2020. The study observed 8,002 participants, ages 45 to 79, who had or were at risk for osteoarthritis, over eight years. Using a carefully designed set of criteria to determine the appropriateness of total knee replacement—including age, symptom severity, and the extent of damage seen on X-rays—the researchers found that more than 90 percent of knees that met the criteria for total replacement were not replaced during the study.
At the opposite end of the spectrum, a smaller but still significant percentage of patients had total knee replacements done too early. The research team determined that 26 percent of the knee replacements performed during the study period were “premature.”
The study didn’t investigate the reasons why people got their surgery early or late. But the findings did reveal that black Americans are almost three times more likely than white Americans to put off getting a knee replacement even when they meet the criteria. People who are overweight or obese are also morelikely to decide against having the procedure.
Those who opted for knee replacements before it was deemed appropriate included younger patients and people who lived alone. Deciding when the time is right to have a knee replacement, it turns out, isn’t as straightforward as you might think, even for orthopedic surgeons. Many factors go into making the decision, including both clinical findings and your personal preferencesand situation.
Risks in waiting too long
Total knee replacement is considered to be elective surgery—a term that suggests you can put the procedure off without consequences. If you delay surgery, stiff and painful knees may cause you to limit or even give up activities like walking or cycling. And the less active you are, the greater your risk of cardiovascular disease, type 2 diabetes, obesity, and other chronic illnesses.
In addition, the muscles around your joints may become weaker and your bones thinner if you have to restrict your activities because of painful knees. That, in turn, could mean that when you do decide to have replacement surgery, your recovery will take longer. And when arthritis damage becomes bad enough, your knees can become deformed. Then walking may put undue wear and tear on other parts of the body, such as the hips.
Putting off surgery may have another indirect but potentially consequential downside. In many cases, to avoid total knee replacement surgery, people choose to get a corticosteroid injection in their knee joint. But emerging evidence suggests this may do more harm than good (see inset below).
Steroid Injection Risks
If you’re considering a steroid injection for hip or knee pain, be aware that it may do more harm than good, according to a study from Boston University in the journal Radiology.
Risks in acting too soon
A total knee replacement involves major surgery with a risk of complications such as infection and bleeding. A premature knee replacement puts you at unnecessary risk with minimal benefit. If you’re relatively young when your knee is replaced, you may need revision surgery to replace or repair part of the artificial joint later in life. That’s because knee replacements last for 15 to 20 years with few problems. But over time, the bond between the implanted joint and bone may fail, causing the artificial joint to loosen. If you have your knee replaced too early, you increase the likelihood of undergoing a potentially avoidable second surgery.
If the pain and damage to the knee are severe enough to seriously compromise your quality of life, then the benefits of surgery may outweigh those risks. But if you can manage the pain and you’re still able to do most of your regular activities, any potential benefits from surgery may not be enough to outweigh the risks.
What’s right for you?
The decision to get a total knee replacement is one you’ll make in consultation with your health care team. Your family should also be involved, since you may need help during the recovery period. The criteria used by the Northwestern team can serve as a guide:
- Your age. If you’re 65 or older, chances are good that your new joint will last a lifetime. It’s also important not to wait too long since the risks of almost any surgery can increase with age.
- Your symptoms. The more pain and stiffness you have in your knee—and the more it interferes with being active—the stronger the argument for getting a replacement.
- X-ray findings. X-ray images of your knee will reveal the extent of arthritis damage and pinpoint the affected parts of the knee.
- The number of knee compartments affected. Our knees have three major compartments: the inside part, the outside part, and the front of the knee between the kneecap and thighbone. In general, if arthritis has damaged just one knee compartment, you may be able to postpone surgery. But if two or three compartments are affected, it may be worth considering a replacement.
- Knee stability. Extensive damage from arthritis can compromise your knee’s stability, increasing your risk of falling or damaging other joints.
Weighing a variety of factors like these is important. If you’re experiencing considerable pain and stiffness but your X-rays don’t show significant damage from arthritis, for example, your doctor may want to investigate other possible causes for your symptoms. If X-rays show extensive knee damage but you aren’t in a lot of pain and can remain active, you might want to delay surgery, since you may not get much benefit from the procedure in terms of pain relief or improved function.
Knee Replacement: How Long Does Recovery Take?
Although recovery times vary, most people can resume normal activities such as sitting, standing, and climbing stairs within three to six weeks after knee replacement surgery.
Your overall health is also a consideration. Many orthopedic surgeons recommend against total knee replacement for people who are extremely obese with a body mass index (BMI) of 40 or higher. Past infections in your knee or some types of previous knee surgeries may also rule out the option of a total knee replacement.
Finally, experts emphasize that it’s important to have realistic expectations about what a knee replacement can—and can’t—offer you. As many as 10 percent of people who undergo knee replacements are dissatisfied with the results, either because they still have lingering pain and stiffness or they don’t recover as much function as they’d hoped.
A total knee replacement won’t allow you to do more than you could before you developed arthritis. You’re likely to be able to walk, cycle, and do activities like golf and low-impact sports after recovering from the procedure. But most surgeons recommend against high-impact activities such as running or sports like football, since they put undue stress on the artificial joint and may cause it to loosen or become painful.
This article first appeared in the April 2020 issue of UC Berkeley Health After 50.
Published April 15, 2020