I just wanted to give everyone an FYI as I NEVER thought in a million years this could happen and it did to my child.
Yesterday, while playing at a friend's house at a birthday party, my 19 month old daughter was on the bottom step (right by the grass) and the friend's dog was on the top step coming down from the deck. Another child at the party threw a ball from the top step for the dog to fetch. The dog took off after the ball and bumped my daughter who was standing on the bottom step. She tried to catch herself and braced with her foot. Her foot stayed steady and her ankle twisted as she fell over onto her bottom into the grass. It was not a hard fall and there were no outward signs of trauma; no scratches, bruises, swelling, bleeding, etc.
She cried and cried (which is very unlike her). She refused to put any weight on her leg. We took her home after about another 45 minutes as my DH and I thought that she was overly tired and just needed a nap. She slept only an hour got up crying and still would not put weight on her leg. We then realized there was a problem. We took her to the ER where she was x-rayed and diagnosed with a buckle fracture of her tibia near the ankle.
So beware of your child twisting their foot while falling off a stair, even if it is not a hard fall, it can break their leg. I never knew this. While at the orthopedic office today, we met another family with a 2 year old girl that had also fallen off a step and broken a leg. Please be careful!