8 Signs You May Need a Knee Replacement

Originally published January 11, 2021

Last updated April 23, 2024

Reading Time: 4 minutes

This common procedure can help reduce pain and restore your ability to move better. But how do you know when it’s time for surgery?

Knee replacement surgery is one of the most successful procedures in all of medicine, according to the American Academy of Orthopaedic Surgeons (AAOS). It’s also very common: More than 790,000 knee replacements are performed each year in the United States. A complete knee replacement — more correctly, a resurfacing — places metal pieces to re-create the surface of the joint, with a plastic separator in between and possibly a plastic resurfacing of the inside of the kneecap (patella).

Although you’ll need a little help afterward, you should be able to begin walking again either the same day or the day after surgery. And the procedure is overwhelmingly successful: The AAOS estimates that 90% of modern total knee replacements are still working more than 15 years after surgery.

How do you know if you need a knee replacement in the first place? Deciding when it’s time is a personal decision between you and your doctor, but there are some factors that make you a more likely candidate for surgery.

1. You have bad arthritis.

Most people who undergo a knee replacement have either osteoarthritis, the wear-and-tear type of arthritis; rheumatoid arthritis, an autoimmune condition that causes joint pain and damage; or postinjury arthritis.

“Osteoarthritis, rheumatoid arthritis and posttraumatic arthritis affect the knee through different mechanisms; however, these different conditions are similar in that they all result in loss of cartilage, which causes pain and loss of motion,” says Nathanael Heckmann, MD, an orthopedic surgeon at Keck Medicine of USC and assistant professor of clinical orthopedic surgery at the Keck School of Medicine of USC. “When these symptoms become severe, knee replacement surgery may provide considerable symptom relief by replacing the worn-out surfaces of the knee.”

2. Nonsurgical treatments are no longer effective.

If you have arthritis of the knee, you’ll probably start with more conservative measures, such as medications, steroid injections or physical therapy, to alleviate your symptoms. But, at some point, they may not be enough.

“Anti-inflammatories, injections and physical therapy are temporary measures to provide pain relief, but they don’t reverse the underlying cause of pain and don’t allow cartilage to regenerate,” Dr. Heckmann says. “As time passes, these arthritic conditions tend to progress in severity, rendering these types of treatments less and less effective.”

At that point, surgery may be an option.

3. Your pain prevents you from doing normal activities or caring for yourself.

If you can’t get relief from other treatments, your knee pain may start interfering with your daily life.

“In general, the timing of a total knee replacement is determined by the impact the knee is having on your quality of life,” says Jay Lieberman, MD, chief of orthopaedic surgery at Keck Medicine and chair and professor of orthopaedic surgery at the Keck School. “If conservative treatments are not working and you have significant pain while walking, you may be a good candidate for surgery.”

4. You have severe pain, even when resting, and you can’t sleep.

According to Dr. Lieberman, pain while at rest that isn’t responding to other measures may make you a good candidate, as well.

“In addition, if you also have consistent pain at night, this can be quite debilitating,” Dr. Lieberman says.

5. Your knee is always swollen.

Swelling is another sign your knee is not responding to other treatments.

“A knee that is consistently swollen despite the use of anti-inflammatory medications, steroid injections and physical therapy suggests degeneration of the cartilage and/or instability of the knee, which can be confirmed with an X-ray,” Lieberman explains. This can make you a candidate for a total knee replacement, he says.

6. Your knee has become deformed.

If your arthritis is advanced, it can affect the way you walk, which can also lead to further problems elsewhere in your body.

“As arthritis progresses, the knee may become bowed or ‘knock-kneed,’” Dr. Heckmann says. “If this type of deformity develops over time, a knee replacement may be indicated.”

In addition, people with arthritis may also lose the ability to straighten their knee, according to Dr. Heckmann. “If this occurs, you should seek an evaluation with an orthopedic surgeon, as this loss of motion may be permanent, even after the knee has been replaced,” he adds.

7. You’re okay with avoiding certain activities afterward.

Patients should know what to expect after knee replacement surgery and understand that regular high-impact activities may not be advisable.

“Total knee replacement is quite successful in enabling patients to return to an active lifestyle — patients can perform all types of recreational activities, including hiking, bicycling, skiing, surfing, tennis and golf,” Dr. Lieberman says. “In general, we do not limit activities but suggest that patients avoid impact activities on a consistent basis to reduce wear of the prosthesis.”

8. You’re of a certain age.

Knee replacement is generally done in older people over 60, in part because younger people’s more active lifestyles may put too much stress on the artificial knee, causing it not to last as long; second replacement surgeries may not be as successful. But knee replacements can be performed in people of all ages, depending on your individual case, so discuss with your doctor whether you’re a good candidate.

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Tina Donvito
Tina Donvito is a freelance writer covering health, culture, travel and parenting.