Keira Knightley has finally explained the mystery injury that prompted the cancellation of her Broadway show, revealing she sprained her wrist on stage.

The British actress is currently starring in a new production of Therese Raquin, which opened on the Great White Way on Thursday night (29Oct15) to lacklustre reviews.

She sparked fears for her health last month (Sep15) when a preview performance of the show was cancelled due to an undisclosed health crisis, and Keira has now explained she injured herself during an action-packed scene with co-star Gabriel Ebert.

"My wrist is not great, it's sprained," she tells the London Evening Standard. "I forgot on stage that I was acting so I launched myself at Gabriel's character, which is not a bright thing to do when I'm 5ft 7in and he's 6ft 4in."

Keira admits the injury is taking longer than expected to heal because she has been busy looking after her baby daughter, Edie.

"Sprains take ages to heal and I have a six-month-old baby which means it's not quite resting in the way that it should, but it's nearly there," she adds.

The actress welcomed her first child with her rocker husband James Righton in the spring (15), and she recently opened up about her joy at becoming a mother.

"The love thing is astonishing. It's a very primal, primal love. That's quite extraordinary," she said. "And the ability to have no sleep and continue going. It's not pleasant - I never thought that I could actually do it for the amount of time that I've done it."

She continues, "Also, I have to say, as a woman, you hate certain parts of your body. You go through those periods where you look in the mirror and you think, 'Oh, if only I had different legs or arms or whatever'. You go through pregnancy and labour and then feeding the kid and you go, 'Wow, my body is totally amazing, and I'm never going to not like it again, because it did this, and this is f**king extraordinary'."