Only about half of people who have a knee or hip replaced see meaningful improvements in pain and disability in the months after surgery, a new study from Canada suggests.
Researchers found people who had worse knee or hip pain to begin with, fewer general health problems and no arthritis outside of the replaced joint were more likely to report benefits.
"I think this study really represents the general picture that often people do not have arthritis in just one joint," said Elena Losina, an orthopedic surgery and arthritis researcher from Brigham and Women's Hospital in Boston.
"It's of course good to set expectations appropriately that if you have three joints affected, doing one procedure is not going to be a miracle," said Losina, who co-wrote a commentary published with the new study.
More than one million people in the U.S. have a knee or hip replaced each year, researchers said - a rate that's expected to continue to grow.
Including hospital fees and the parts themselves, the procedures cost $20,000 to $25,000 and are typically covered by insurance.
Despite the rising popularity of joint replacement, uncertainty remains about which patients have the most to gain and who fares best post-surgery. So a team led by Dr. Gillian Hawker from the University of Toronto tracked about 2,400 older adults with osteoarthritis or inflammatory arthritis in Ontario, Canada, to see who went on to get surgery and how they did.
From the start of the study in 1996 through early 2011, 479 of them had a knee or hip replaced, including 202 who underwent elective surgery and had before and after pain and disability information available for analysis.
Most surgery patients were women with pain in more than one joint, and over 80 percent were overweight or obese.
By a year or two after surgery, the average person had a 10-point improvement in pain and disability from a pre-surgery score of 46.5 out of 100, the research team wrote in Arthritis and Rheumatism.
A nine-point improvement is considered the "minimal important difference" in symptoms, and about 54 percent of joint-replacement patients hit that target.
Unlike general health and other joint problems, people's weight did not predict how they did after a knee or hip replacement, Hawker and her colleagues found.
Losina said that even if a first joint replacement leaves people with some pain and disability, it may help them make incremental steps toward better health.
And doctors may need to realize that until some people get each of their painful joints replaced - not just one knee or hip - they're not going to have optimal outcomes, according to Hawker.
"We have to look at the whole patient, not just a single joint," she told Reuters Health.
Researchers said the new findings provide more evidence for patients and their doctors to use while discussing the pros and cons of knee and hip replacement.
"This is not an easy surgery, it's an expensive surgery, and I think people should understand what they are getting into and what are the expected outcomes," Losina told Reuters Health.
Andrew Judge, who has studied joint replacement outcomes at the University of Oxford in the UK, agreed these kinds of findings are important to help inform doctor-patient decision making.
"Further research is required in other large datasets in order to confirm these findings, and to identify other key determinants of good outcomes, to inform the development of a future clinical risk prediction tool," he told Reuters Health in an email.
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