Another Reason to Run
Running is good for you! If it wasn't kids would not do it, and have fun (many younger kids are efficient runners). It's what we call an Activity of Daily Living, and no it's not bad for your knees.
A recent study of almost 3000 people 25 years ago and again recently were asked to run as long as they could on the treadmill. Those who ran longer performed better at cognitive testing for memory and thinking skills. The BBC recap is here. Exercise is for complete health!