My 6 year old niece was skiing with us and fell down. She says her arm is killing her. How can I tell if it’s broken? The closest emergency room is 50 miles from here.

It may not be easy to tell if her arm is broken unless she has a break in a bone that is not aligned and then you would be able to visually see a deformity in her arm.  If it is not initially obvious, gently touch her bones and see if there is one point that is tender.  If she does have a specific point that hurts chances are she has a fracture.  Any swelling in the elbow also is concerning for a fracture.

If she refuses to move her arm, and continues to have pain, the best answer is to go the 50 miles to the closest emergency room.  An elbow fracture or upper arm fracture can be very dangerous as there are both a nerve and an artery that can be damaged during a fall.