Looking for a children's fantasy novel about a poor boy working at a circus who rescues a Chinese girl with bound feet who's a prisoner in one of the attractions. Takes place in medieval Europe, I think. They're on the run and get rescued by a witch or an old woman who heals the girl's feet by breaking the bones and then teaches her how to walk again. The boy and the girl go on a quest together. There may be a dragon involved. Wasn't a picture book and it had chapters. Read it between 2002 and 2008, but was probably published way earlier. Wish I had more info, thanks!