She has shoes on, which this is the first year she has had back shoes on. Which is probably irrelivent, but when i'm riding her all of a sudden she will stop up and hold her back left leg up for a few seconds, like she hurt it. There is nothing in around her frog or stuck in around her shoe and when I clean it out she doesn't flinch. I can trot and canter with her and it doesn't bother her. Could she have bruised her from from cantering and hitting a rock? Or when she had her shoes on could he have taking a piece off her frog by an accident and it be soft and hurt. I'm just confused because she doesn't do it all the time.