Conventional wisdom holds that running will eventually trash your knees by wearing down their cartilage, ultimately leading to arthritis. But that may have to be revised: Recent studies suggest that runners may have healthier knees in old age than their sedentary peers, reports Gretchen Reynolds for the New York Times. Scientists theorize that runners’ knees develop a “motion groove” that conditions the cartilage to support rhythmic stress, protecting it into old age.
To wit, one 2008 Stanford study found that while runners in their 50s and 60s had more arthritic symptoms than a control group, they were less likely to develop the full-blown condition in their 70s and 80s. The exception is those with a knee injury in their history, which can upset the alignment and allow the joint to fall into motions that wear away the cartilage. So to keep from ruining your knees, says Reynolds, keep running, but avoid injury—or, in the event of one, see a doctor.