Replacement of both knees at once is good option for some

Q. I have severe osteoarthritis in both knees. Should I have both knees replaced at one time, or separately?

A. Knee replacement is a major operation and requires a hospital stay. During the procedure, the surgeon removes damaged sections of your shin bone and thigh bone. He or she carefully cuts the bone to precisely fit the shape of the replacement implants, then attaches the artificial joint at the knee. (I've put an illustration of the procedure on my website, AskDoctorK.com.)

Knee replacement also requires a rigorous program of physical therapy and rehabilitation after surgery. It's just plain hard work. You need to be ready for that, as well.

Should you consider having both knees replaced during a single surgery (simultaneous replacement)? If you are in good health, it's worth talking to your doctor about replacing both knees at once.

There are several benefits to simultaneous replacement. These include going under anesthesia only once and a shorter total hospitalization. You'll also have only one — albeit, prolonged — rehabilitation. This will allow you to resume normal activities sooner than two separate surgeries.

Replacing both knees at once is also a good option if both of your knee joints are in poor condition. That's because during recovery from the replacement of one knee, you need the other knee to work harder. If the other knee hurts when you place weight on it, this will make it difficult for you during physical therapy and would also slow your recovery. To do well in rehabilitation after simultaneous surgery, however, you need enough arm strength to cope while you can't stand on either leg.

Simultaneous replacement slightly increases the risk of blood clots or heart attack. However, such complications are rare. Still, simultaneous replacement is not for everyone. It is not recommended for patients with heart or lung disease or people over 80. If you have significant medical risks, you are probably better off having two separate operations.

There are also benefits to separate operations months apart. These include a reduced risk of post-surgical infection and less chance of needing a second surgery to fix problems.

So having both knees replaced simultaneously surely is a reasonable option for many people. You and your doctor need to consider all of the issues mentioned above.

Personally, I'm under 80; my arms are strong, and I have fun using crutches. So, if both of my knees had come to the end of the road and needed replacement, and if I had no underlying heart or lung disease, I'd probably choose simultaneous replacement of both knees.

Whether you have your knees replaced together or separately, you'll need to actively participate in a rehabilitation program. This will be a major factor in the success of your implant.

Ÿ Dr. Komaroff is a physician and professor at Harvard Medical School. Send questions to AskDoctorK.com.