"I have, like, a bruised bone... What happened was that one of the dancers' backs was slippery from sweat and the lights and everything," Contactmusic quoted her as saying at Ellen DeGeneres' TV chat show.
She added: "We never bargained for that because they always had T-shirts on in rehearsal... and when I stepped on their backs, my feet were wet, so when I landed they slipped from under me."
The 'Waiting for Tonight' hitmaker mentioned that she did not immediately realize she had fallen.
She said: "That's kinda what I thought the rest of the performance: 'Did I fall...?' It happened so fast and I was up and all I could think was, 'I have to get to the next beat... I have to do this dance solo, right now.' I had no time to think about it.
"I did the rest of the performance, walked out, was like, 'Yeah...!' And one of the dancers was like, 'Are you OK?' And I'm like, 'Oh my God, that's right, I fell...!' It happened."