Knee replacement surgery is increasingly common among people over 80 sidelined with knee pain, and the procedure isn’t as hazardous for them as often assumed. That’s the main message from a new study of more than 1.7 million seniors who underwent knee replacement surgery. The findings come as no surprise to Dr. Thomas Fleeter, whose oldest knee replacement patient was 96. Age is just a number when it comes to knee replacement surgery, said Fleeter, an orthopedic surgeon with offices in Reston and Centreville, Va. He was not involved with the new study. “Nobody wants to live in pain, and one of the greatest fears of elderly people is being dependent,” he said. These folks want to go to the grocery store, see their grandchildren, travel, garden and live their lives to the fullest, he added. For many of them, knee replacement surgery can help meet these goals. Octogenarians do have longer …