More than half of all older adults in the U.S. have arthritis. Most often it’s osteoarthritis (OA)—where the cartilage between joints wears down, causing swelling, pain, and disability in some.

Since the 1960s, people with severe OA have had the option of surgery to replace certain painful joints with prosthetics made of metal, ceramic, and plastic. Knee and hip replacements are now the third and fourth most common surgeries, respectively, in U.S. hospitals, behind cesarean sections and circumcisions.

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But while often highly successful, a joint replacement may not eliminate all pain or restore full range of motion in a hip or knee. “We can’t take someone who is doing awful and suddenly make them perfect,” says David Jevsevar, M.D., chair of the department of orthopedics at the Geisel School of Medicine at Dartmouth.

Overall, hip replacement results are better than those for knee replacement. Only about 1 in 10 people who have hip replacement report persistent pain or dissatisfaction after surgery. One in 5 knee replacement recipients say they have continuing pain afterward or are unhappy with the outcome.

Both surgeries carry some risks, and not everyone is a candidate. Though some research suggests that obese people may gain significant benefits from joint replacement, being obese raises the risk of infection and other surgical complications. And both smoking and diabetes are associated with an increased likelihood of surgery-related infections.

Here, what you need to know about the benefits and potential downsides of joint replacement:

When to Consider Surgery

If you have hip or knee OA, turn first to conservative measures. Depending on your level of pain or difficulty functioning, these may include exercise, physical therapy, weight loss, the use of over-the-counter nonsteroidal anti-inflammatories (NSAIDs) such as ibuprofen (Motrin IB and generic) and naproxen (Aleve and generic), and assistive devices such as canes.

For joint replacement, it’s ideal to hold off until you’re at an age when a prosthetic device is likely to last the rest of your life. (They usually last 10 to 15 years.)

The younger you are when you have the surgery, the higher the chance that the new joint will ultimately give out, leading to revision surgery to replace the device. According to a large 2017 study, men in their early 50s who received hip or knee replacement were most likely to require a revision. After age 70, the risk of revision dropped to about 5 percent.

Yet you don’t want to put it off so long that you’re too debilitated to gain back substantial function after surgery. “We don’t have a way of predicting the sweet spot,” says Mary O’Connor, M.D., director of the Center for Musculoskeletal Care at Yale School of Medicine and Yale New Haven Hospital. But when pain or limited mobility begin to inhibit your daily routine, it’s time to talk with your doctor.

Set Yourself Up for Success

If you and your doctor think joint replacement is reasonable, give yourself time beforehand to deal with health issues that may interfere­­—such as obesity or uncontrolled diabetes. And take these steps:

Pick an experienced surgeon who frequently performs joint replacement and has a low complication rate: At least 50 surgeries a year and a 3 percent or lower complication rate are good benchmarks. The medical facility you choose should do at least 400 joint replacements annually.

Because a key risk of surgery is infection, ask about the facility’s overall infection rate (it should be less than 1 percent). Or check Consumer Reports’ hospital ratings.

Find out about recalls. Ask your surgeon whether the device he or she is planning to use has ever been recalled, advises Lisa McGiffert, director of the Safe Patient Project at Consumers Union, the policy and mobilization division of Consumer Reports. (Occasionally, recalled devices are still used, she says.) And request the unique device identifier for your implant in case it is recalled in the future.

In addition, make sure you don’t have an allergy or a sensitivity to any of the materials in your device and that your surgeon isn’t planning to use a metal-on-metal implant. These have caused health problems in some people.

When it comes to techniques, don’t be dazzled by robotic or minimally invasive surgeries—which use shorter incisions—says Matthew Kraay, M.D., professor of orthopedic surgery at Case Western Reserve University School of Medicine. They haven’t been shown to be more effective than standard methods, and surgeons may be less familiar with them.

Ask your doctors how they’ll manage your pain after the procedure. A multimodal pain management program is best, Kraay says. That means a combination of techniques, such as nerve blocks, epidural injections, and NSAIDs. This approach can reduce the need for opioid medications.

If your doctor recommends outpatient joint replacement, be sure it’s right for you before you agree. The best candidates for such same-day surgery, Kraay says, are people in top health who are highly motivated to take on their rehab at home.

The Best Healing Strategies

Most people used to need weeks in a hospital after a total joint replacement, Kraay says. Now those who have hospital-based surgery are increasingly likely to be discharged after a few days­—and to go straight home instead of to a rehab facility.

That’s better, experts say, because at home your risk of infection is lower and you’re usually more comfortable. (If you had particularly limited mobility beforehand or had both knees replaced at the same time, you may need to spend some time in rehab afterward.)

Be aware that, generally, it’s easier to recover from hip replacement than from knee replacement, says Daniel Riddle, P.T., Ph.D., a professor of physical therapy at Virginia Commonwealth University.

Because the hip is a much simpler joint than the knee, and the surgery much more straightforward, people may not even need formal physical therapy after hospital discharge. 

You’ll need to pay attention to your doctor’s instructions, Riddle says, but usually your normal activities—such as bathing, cooking, and climbing stairs—will provide your hip enough movement to keep your recovery on track. Most people will be about 90 percent recovered within six to eight weeks after surgery, with more small improvements over the next year.

With knee surgery, you can expect to do physical therapy two or three times a week for about a month and exercises at home daily. Riddle says the average person will need eight weeks to recover by about 80 percent. Full recovery may take up to 18 months.

In either case, to help your hip or knee implant last as long as possible, you should avoid high-impact activities, such as running, jogging, and heavy lifting. Instead, opt for exercise such as biking, swimming, or using an elliptical machine. Riddle recommends trying to walk or exercise every day because it will help you heal and stay mobile long-term.

Editor’s Note: This article also appeared in the February 2018 issue of Consumer Reports On Health