Knee and titanium hinge joint. Isolated on white (alex-mit/Getty Images/iStockphoto)

You might think that knee and hip replacements would be an everyday affair. After all, they’re among the most common operations in the United States, with about 1 million done every year. And with that number set to quadruple by 2030, they look to be practically a rite of passage into the golden years.

But that popularity has not bred consensus among surgeons. The choice of prosthetic, the operating procedure and other factors can vary from one surgeon or hospital to the next. And that variation can have an important impact on outcomes.

One example: Your chances of a post-surgical infection. Consumer Reports’ assessment of data from hospitals in California found striking differences in infection rates, even among institutions in the same area. St. John’s Health Center in Santa Monica, for example, had a positive rating (68 percent better than the national average for knee infections) while nearby Los Alamitos Medical Center had an infection rate that was more than twice the national average.

Here’s what else matters most:

Doctors and hospitals

In an era when your options include 3-D-printed knees and robotic surgical assistants, the doctor’s experience still matters most. “It’s hard to find a more powerful predictor of outcome than volume,” says Jeffrey N. Katz, director of the Orthopaedic and Arthritis Center for Outcomes Research at Brigham and Women’s Hospital in Boston. In most hospitals “there’s somebody who is spending a lot of time doing replacements,” Katz says. “That’s the person you want.”

A hospital’s experience matters, too. Those with the most experience tend to have support staff that can help manage pain, speed recovery and watch for trouble.

Ask prospective surgeons how many replacements they have done in the past year (ideally, you want someone with at least 50) and about complication rates (look for 3 percent or less). Check on the hospital’s infection rate, too (it should be lower than 1 percent) and its rehabilitation plan. (A hospital that gets patients moving soon after surgery cuts the risk of complications and hastens recovery.)

Procedures and prosthetics

Joint replacement has seen astounding advances in recent years in the types of prosthetics available and the techniques by which they are implanted. Some hospitals pitch 3-D-printed implants that promise a tailor-made fit or robotic-assisted procedures that allow “minimally invasive” surgery requiring smaller cuts and less drilling in bone. But the jury is still out on such advances; so far, only a small number of surgeons opt for either.

“They sound cool,” Katz says, “but there’s no evidence that they’re any better than what we’ve been doing for ages.” What’s more, they may be more expensive.

If you’re considering surgery, avoid being swayed by the newfangled. “You shouldn’t focus too much on the technical details,” Katz says. “If you do, you may end up in a poor-quality hospital with a poor-quality surgeon because they offer the one gadget you think you need.”

Recalls and revisions

Implants are often allowed on the market without review by the Food and Drug Administration, says Lisa McGiffert, director of Consumer Reports’ Safe Patient Project. And all major knee and hip manufacturers have had a product recalled in the past decade, she says.

When an implanted device is recalled, the cost of replacing it is often borne by patients and their insurers, not the device maker. The revision tends to cost more and be less successful than the original. It can also result in longer hospital stays and additional surgeries beyond the revision.

McGiffert argues that knee and hip implants should come with a warranty. Until they do, you should do your homework: Ask whether the device the surgeon uses has been recalled at any point, and if so, why? It’s not a silly question, McGiffert says: Recalled devices are sometimes used. You should also find out what the device is made of. (They’re usually made of metal alloys, ceramic or plastic.) And ask for device documentation, including the manufacturer, model name and product inserts. Keep the information with your medical records.

Copyright 2016. Consumers Union of United States Inc.

For further guidance, go to www.ConsumerReports.org/Health, where more detailed information, including CR’s ratings of prescription drugs, treatments, hospitals and healthy-living products, is available to subscribers.