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Why should the strength of your hips affect your knees? It’s all about stability. Experts have long known that having a strong core (aka the trunk of your body) is essential to avoiding pain and injury, but until recently, core meant abs and back; the hip muscles weren’t included. That’s changed, thanks to a slew of recent studies confirming that the hips play a key role in balancing, aligning and supporting body parts from the low back on down. “Weak hip muscles are an often-overlooked cause not only of common sports-related injuries, such as runner’s knee, but also of low-back pain in nonathletes,” says Reed Ferber, PhD, director of the University of Calgary’s Running Injury Clinic and a leading researcher on hip strength. –SOURCE