An elderly man participates in physical therapy for his knee.
By staging knee replacements a few days or weeks apart, physical therapy and rehabilitation becomes easier to manage. (For Spectrum Health Beat)

Everyone seems to know someone who’s had knee replacement surgery.

The procedure is on the rise for both sexes, with the rate of total knee replacement doubling among women age 45 and older, according to the Centers for Disease Control and Prevention.

But just as no two patients are alike, not all knee replacement surgeries are the same.

So when a patient with two bad knees asks whether she can have both knees replaced at once—a surgery known as simultaneous bilateral knee replacement—the answer isn’t a simple yes or no.

What’s her age? How is her overall health? How quickly does she want to get home after surgery? And how bad are the two knees?

All of these questions come into play, according to Susan Day, MD, an orthopaedic surgeon and knee replacement specialist with Spectrum Health Medical Group.

“It makes a difference whether it’s a partial or a total (knee replacement),” Dr. Day said. “And it makes a difference what kind of patient you’re dealing with” and what the patient’s goals are.

Total knee replacements

Simultaneous bilateral

“There are some folks, I think it might make sense to do two (total replacements) at the same time, just because they have such deformity of both knees,” Dr. Day said.

Although painful, the rehabilitation process is easier for these patients, she said, because the two knees can work together. You can’t ride an exercise bike, for example, with one knee needing rehab and the other knee still waiting for surgery and perhaps unable to straighten all the way.

For most patients, however, having both replaced at once is not the best option.

“Simultaneous bilateral knee replacement is sometimes really painful and difficult for the patient,” Dr. Day said.

What’s more, some patients’ general health makes it “just too risky to do two under the same anesthetic.”

Health conditions that increase the risk for post-operative complications include morbid obesity, coronary artery disease, diabetes, kidney failure, obstructive pulmonary disease and advanced age.

Staged two days apart

Dr. Day’s preference, when a patient needs two total knee replacements, is to stage the surgeries two days apart. She’s been using this strategy for about 10 years.

Compared to replacing both knees at once, spacing the surgeries two days apart has several advantages, Dr. Day said:

  • It lowers the risk of complications, such as increased blood loss during surgery or persistent wound drainage.
  • It’s less painful for patients because it allows the pain in the first knee to fade a bit before the second knee is operated on.
  • It lets patients rehab both knees at the same time, shortening the total recovery time.
  • It allows doctors to postpone or cancel the second surgery if a medical issue arises that makes a second surgery inadvisable.

But the two-days-apart approach isn’t right for all patients. Some need time to rehab the first knee before having the second one replaced.

Others simply want to get home as soon as possible, Dr. Day said.

“If you do one knee, most of those folks will go home. If you do two, whether under the same anesthetic or separated by a couple of days, most of those folks will go to the rehab unit. … For some folks, that’s a deal breaker. They don’t want to go to rehab; they want to go home.”

Staged six weeks apart

Staging the two knee replacement surgeries six weeks apart is another option. This is the strategy Bryan Kamps, MD, prefers. Dr. Kamps is an orthopaedic surgeon at Spectrum Health Medical Group specializing in knee and hip replacements.

“It’s hard to get two knees working the way they should, both of them, at the same time,” he said. “It’s harder to get moving.”

Separating the two surgeries by six weeks lets patients do their rehab either with a home health aid or at a physical therapy center.

Partial knee replacements

In a partial knee replacement, only part of a damaged knee is replaced. Because this procedure is less invasive than a total knee replacement, it allows for different options, Dr. Day said.

“With partial replacements I do them bilateral, under the same anesthetic,” she said. “There’s less blood loss associated with a partial than with a full. And those patients usually I just keep overnight in the hospital and they go home the next day.”

Doing two partial knee replacements at once is a common procedure for Dr. Day, who, like Dr. Kamps, performs all surgeries at the Center for Joint Replacement at Spectrum Health Blodgett Hospital.

The bottom line

The takeaway for patients with two bum knees is if they ask to have both replaced in a single surgery, the answer might be complicated.

“Ultimately, it’s a discussion between the patient and the doctor—and the primary care physician,” Dr. Day said. “The most important thing is to have an uneventful surgery.”

Thinking about knee replacement surgery? Read our Hip and Knee Replacement Quality Reports.