 In the scene where a young man takes Bette Davis and does a  "Jitterbug" dance, she felt he was holding back in rehearsals, and  told him to treat her like an experienced dance partner. When the  cameras rolled, he pulled out all the stops and swung her around and  she fell on her knee. As she finishes her song, you see her limping  out of the night club set and she leans against a post rubbing her  knee. This was a real injury, but she finished the song despite the  pain. There were no retakes possible.