After Garbo, Leigh, no defining Anna Karenina: Knightley LOS ANGELES (Reuters) - Film adaptations of "Anna Karenina" have featured the likes of Greta Garbo and Vivien Leigh, but Keira Knightley isn't fazed about measuring up to such silver screen luminaries with a new cinematic take on Leo Tolstoy's classic novel. The British actress's turn in the title role in the timeless story about a beautiful married socialite in 1870s Russia who embarks on a passionate affair with a cavalry officer, follows the 1935 version starring Garbo and the 1948 film with Leigh. It is released in the United States on Friday. "Although there have been many famous actresses play her, there's never been a definitive version of 'Anna Karenina,'" Knightley said in an interview. I think it's partly because of the relationship you have with the character. She poses more questions than she answers, so it's always open to different interpretation. Knightley stars opposite Jude Law as her husband, and Aaron Taylor-Johnson as the dashing Count Vronsky, and teams up again with filmmaker Joe Wright in their third film together after previous book-to-film collaborations with 2007's "Atonement" and 2005's "Pride & Prejudice." The film debuted at the Toronto film festival to warm reviews for Knightley's performance. Critics have said the film is overall technically and visually accomplished but lacks a cohesive emotional punch. Adapted by playwright Tom Stoppard, Wright's "Anna Karenina" takes place mostly in a theater setting and sees the title character more high-strung and less sympathetic than in previous incarnations. The director said he cast Knightley, 27, because he felt she could tap into all the internal elements of Anna. "She was 18 when we made 'Pride & Prejudice', just a kid," said Wright. I've seen her develop from stunning ingénue to great actress. I felt that she was stronger, braver, even less conforming than she had been before. Knightley, newly engaged to musician James Righton, said she stood in moral condemnation over Anna,- "But am I any better than her? "I think we're all her," she added. That is why she's so terrifying. We all have bits of her personality within us. We can be wonderful, we can be loving, we can be full of laughter and full of life, and we can also be deceitful, malicious, needy and full of rage. While "Karenina" cements the perception of Knightley as a go-to actress for period pieces that also includes films like 2008's "The Duchess" and 2004's "King Arthur," her career wasn't always associated with roles grounded in the past. Knightley spent the 1990s working in the British film and television industry before gaining international attention in the 2002 teenage soccer movie "Bend it Like Beckham." After that, the actress said she was offered "an awful lot" of films in the teenage genre. "The one thing that I knew right from the beginning was that I didn't want to get into those high school movies," she said. I was never that interested in being a teenager. I was always interested in worlds away from my own. She credits the "massive" success of the "Pirates of the Caribbean" franchise - which saw her play Elizabeth Swan in the first three installments - as an integral part of her career and "a lot of the reason I was able to do other kinds of smaller films, because my name would help in financing them." Coming up, Knightley takes a turn away from costume dramas, in "Can A Song Save Your Life?" - a musical drama that sees her starring as an aspiring singer who meets a down-on-his-luck record producer, played by Mark Ruffalo. She's currently shooting a reboot of the Tom Clancy thriller "Jack Ryan." "I got to the end of 'Anna Karenina' and I realized that I'd done about five years of work where I pretty much died in every movie and it was all very dark," she said. So I thought, okay, I want this year to be the year of positivity and pure entertainment. Reporting by Zorianna Kit, editing by Christine Kearney and Patricia Reaney