7 year old son woke up this morning suddenly unable to walk. No pain sitting or laying down, but pain in both legs when standing. No recent trauma to legs. No fever , but both sisters have had fevers this past week. All 3 kids have had coughing and runny nose . He is an active, athletic child who is on a competitive swim team and plays recreational soccer and tennis. He had no practices or games since Monday so shouldn t be any kind of overexertion.