Knee replacements more than double

Knee replacement surgeries have more than doubled in two decades in the United States as older Americans strive to stay active later in life, a study has found.

Total knee replacement procedures rose 162 percent from 1991 to 2010, while the number of procedures to repair a previously implanted artificial knee joint, called revision, jumped 106 percent, according to research released in the Journal of the American Medical Association.

About 600,000 total knee replacement procedures, done to relieve severe knee arthritis, are performed each year in the United States, costing about $9 billion a year, the research showed.

About 60 percent of the procedures are paid for by Medicare, the federal government health program for the elderly and disabled, said Peter Cram, the lead study author. The study suggests the success of the surgery may need to be weighed against the increasing costs, he said.

"The growth in knee replacements encapsulates the challenges of controlling spending in the Medicare program," said Cram, associate professor of general internal medicine at the University of Iowa Carver College of Medicine. "It is an effective surgery."

The public-health issue, Cram said, is that "a procedure that is great in small numbers is financially devastating to the Medicare program and the federal government in the long term."

Researchers looked at 3.27 million Medicare patients who underwent total knee replacement procedures and 318,563 who had revision surgery from 1991, the first year data were available, to 2010. The number of annual knee replacements rose to 243,802 in 2010, or 62.1 procedures per 10,000 Medicare enrollees, from 93,230 in 1991, or 31.2 procedures per 10,000 Medicare enrollees.