One of the biggest innovations came in the late 1990s and early 2000s — just in time for the marathon-running, tennis-playing boomers to start showing signs of wear and tear. “The industry figured out a way to make the implants better,” said Robert Cohen, president of digital, robotics and enabling technologies for Stryker’s Orthopaedic joint replacement division in Mahwah, N.J. “We used the exact same plastic — relatively soft, but durable — and put it through a post process, of heat and radiation, that made it even stronger.” The “highly cross-linked polyethylene” implants significantly reduced the need for revision surgery. “One of the main reasons for revision was the polyethylene breaking down in the replacement joint,” he said. Thanks to the advent of the stronger, more durable material, he says, “we’ve pretty much eliminated that.” The new implants also helped lead to faster recovery times. Dr. Matthew Sloan at the University of Pennsylvania, the lead author of the 2018 study, said that “among the older patients, the big driver is the desire to stay active.”