"I have a bruised bone," she tells Ellen DeGeneres for an episode of the talk show to air Thursday. "What happened was one of the dancers' backs was slippery from sweat and lights and everything. We never bargained for that because they always had T-shirts on in rehearsal.
"So they were barebacked, didn't have shirts on for the performance, and when I stepped on their backs my feet got wet. So when I landed. it just slipped from under me."
But Lopez, 40, credits her quick recovery to the excitement of the moment. "That's kind what I felt the rest of the performance: Did I fall? It happened so fast," she says. "I was up and all I could think was, I have to get the next beat. I have to do this dance solo right now. I had no time to think about it."
Only afterward did she realize what had happened.
"Then I get to the back, and one the dancers was like, 'Are you OK?' Oh my god that's right, I fell," she says. "It was awful, but, you know, it happened."