A new study has shed light on the number of Americans who are living with artificial knees or hips: more than 7 million people in the United States have had knee or hip replacement surgeries – 4.7 million knee replacements (TKR) and 2.5 million hip replacements (THR). Mayo Clinic researchers, who presented their findings at the American Academy of Orthopaedic Surgeons annual conference earlier this month, say the study highlights the need of the health care system to prepare for the ongoing care these patients are likely to need as they age.

Previous studies have shown about 1 million new total knee and hip replacements are done in the U.S. every year – and that number is expected to grow – but until now there has been very limited information on the total number of patients who are living with one of the prosthetic devices.

The researchers say the numbers are quite large. “These numbers tell us roughly 1.5 times as many people have had a joint replacement in America as heart failure at any one time,” explains the study’s senior author, Daniel Berry, MD, professor of orthopaedics at Mayo Clinic in Rochester, Minn. He says the estimates are “within the same ballpark” as coronary heart disease and “much higher” than stroke.

To determine these numbers, researchers looked at incidence rates for total hip and knee replacements dating back to 1969 and combined that with mortality rates.

Among their findings:

  • More people have new knees than new hips. Approximately 1.5 percent of Americans are living with a knee replacement and 0.8 percent with a hip replacement
  • More women than men have joint implants. Almost twice as many women have artificial knees as men (3 million women and 1.7 million men) and slightly more women have artificial hips compared to men (1.4 million women and 1.1 million men).
  • Age is a factor. The percentage of people with an artificial hip or knee increases with age: Among adults age 50 and older, 2.3 percent and 4.6 percent have an artificial hip or knee respectively; among adults age 80 those figures rise to 6 percent and 10 percent respectively.

Dr. Berry says these statistics suggest the dramatic effect these procedures have had on a fairly large segment of the population. “If it weren’t for this technology, there would be roughly 7 million Americans much less mobile and much less independent and in more discomfort, so it tells you the degree to which this operation transforms the lives of people with arthritis,” he says.

But with these benefits comes the ongoing need to care for these patients.