Hi I Have A 13 Yr Old Very Active Boy.

Hi I have a 13 yr old very active boy. Who started having knee pain on Friday. There is no bruising it is tender to touch and also very warm to touch. And he has complained about it all weekend that it hurts when he bends his knee. Now here we are Monday morning and it hurts to even stand on it no falls that were great enough for him to remember. And he plays lacrosse