My 8 year old athletic son has slight flattening of the feet and wears shoe inserts prescribed by the podiatrist. He still experiences slight to moderate ankle sprains almost every couple of weeks. However, instead of the sides of his ankle hurting the pain is on the top of the foot where the large tendon(s) is (are).  By looking at his feet it seems that the two tendons on top of the foot are further seperated than mine as a larger adult. The othopedic and podiatrist can't find anything wrong with him. But he's always in pain when he goes outside for long periods of time playing hard. As a side note, this basketball season he fractured his heel, after coming down on another players foot from a rebound. He was in a cast for 6 weeks. The ankle pain is not new, its been hurting him well over a year.