It's time to stop blaming your knee pain on running, especially if it's why your only exercise is a circuit between the couch and the fridge. Recent research shows that running won’t ruin your knees — but being weak will. "Too many runners only run," says Diana Garrett, DPT, a physical therapist based in Santa Monica. "I think strength training is crucial for injury prevention." Research shows even higher rates of knee pain in people with not only weakness, but a high body mass index on top of it. And chances are, the problem isn't just in the knees in the first place. "Function of the lower extremity is dictated by motions at the low back, hip, knee, ankle and foot,” says Stephen Chao, DPT, a physical therapist and an associate clinical professor at SUNY Stony Brook. "A breakdown at any one of these points, even a minor one, can be a weak point that will stress the knee given the roughly 1,000 steps one takes each mile they run."

To save yourself from a vicious circle that keeps you off the running trail, here’s how to build a better lower body, and by extension a set of knees that will last you for hundreds of thousands of miles.