"Don't worry about it," mothers often tell children complaining of leg aches. "It's just growing pains."
Or is it? Growing pains are interesting, for in one way they are real but in another way, they don’t really exist. Growing pains are minor, unspecified aches and pains (often in the arms or legs) reported by young children.
For the rest of the story: http://www.lifeslittlemysteries.com/263-what-are-growing-pains.html