Clarke, 28, opened up about the mystery injury while attending the premiere of the science-fiction "Terminator Genisys", reported ET online.
"I fractured my hip break dancing with Arnold Schwarzenegger," the "Game of Thrones" star said when asked about the injury.
Clarke, who is all set to reprise the role of Sarah Conor which was orginally played by Linda Hamilton in the previous two "Terminator" films, hopes Hamilton watches her performance and likes it.
"I haven't at all. I just really hope she watches it and likes it," the actress said.