From page 2: "The study also showed that people cannot use the risk of injury as an excuse not to run -- the runners had fewer injuries of all kinds, including

From page 2: "The study also showed that people cannot use the risk of injury as an excuse not to run -- the runners had fewer injuries of all kinds, including to their knees." In fact, other papers I've read have said that runners and cross-country skiers maintain bone density and joint lubrication into old age, while swimmers and cyclers do not.