Most knee replacements are considered successful, and the procedure is known for being safe and cost-effective. Rates of the surgery doubled from 1999 to 2008, with 3.5 million procedures a year expected by 2030.
But doctors are increasingly concerned that the procedure is overused and that its benefits have been oversold.
Research suggests that up to one-third of those who have knees replaced continue to experience chronic pain, while 1 in 5 are dissatisfied with the results. A study published last year in the BMJ found that knee replacement had “minimal effects on quality of life,” especially for patients with less severe arthritis.
One-third of patients who undergo knee replacement may not even be appropriate candidates for the procedure, because their arthritis symptoms aren’t severe enough to merit aggressive intervention, according to a 2014 study in Arthritis & Rheumatology.
“We do too many knee replacements,” said James Rickert, president of the Society for Patient Centered Orthopedics, which advocates for affordable health care. “People will argue about the exact amount. But hardly anyone would argue that we don’t do too many.”
Although Americans are aging and getting heavier, those factors alone don’t explain the explosive growth in knee replacement. The increase may be fueled by a higher rate of injuries among younger patients and doctors’ greater willingness to operate on younger people, such as those in their 50s and early 60s, said Rickert, an orthopedic surgeon in Bedford, Ind. That shift has occurred because new implants can last longer — perhaps 20 years — before wearing out.
Yet even the newest models don’t last forever. Over time, implants can loosen and detach from the bone, causing pain. Plastic components of the artificial knee slowly wear out, creating debris that can cause inflammation. The wear and tear can cause the knee to break. Patients who remain obese after surgery can put extra pressure on implants, further shortening their lifespan.
The younger patients are, the more likely they are to “outlive” their knee implants and require a second surgery. Such “revision” procedures are more difficult to perform for many reasons, including the presence of scar tissue from the original surgery. Bone cement used in the first surgery also can be difficult to extract, and bones can fracture as the older artificial knee is removed, Rickert said.
Rickert said that some patients are offered surgery they don’t need and that money can be a factor.
Knee replacements, which cost $31,000 on average, are “really crucial to the financial health of hospitals and doctors’ practices,” he said. “The doctor earns a lot more if they do the surgery.”
Yet surgery isn’t the only way to treat arthritis.
Patients with early disease often benefit from over-the-counter pain relievers, dietary advice, physical therapy and education about their condition, said Daniel Riddle, a physical therapy researcher and professor at Virginia Commonwealth University in Richmond.
Studies show that these approaches can even help people with more severe arthritis.
In a study published in Osteoarthritis and Cartilage in April, researchers compared surgical and non-surgical treatments in 100 older patients eligible for knee replacement.
Over two years, all of the patients improved, whether they were offered surgery or a combination of non-surgical therapies. Patients randomly assigned to undergo immediate knee replacement did better, improving twice as much as those given combination therapy, as measured on standard medical tests of pain and functioning.
But surgery also carried risks. Surgical patients developed four times as many complications, including infections, blood clots or knee stiffness severe enough to require another medical procedure under anesthesia. In general, 1 in every 100 to 200 patients who undergo a knee replacement die within 90 days of surgery.
Significantly, most of those treated with non-surgical therapies were satisfied with their progress. Although all were eligible to have knee replacement later, two-thirds chose not to do it.