Nicole Kidman sported two "skinned knees" during a Los Angeles workout that may show the actor had a series of fat-busting injections, the Daily Mail reported.

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Dr. Lucy Glancey of City SkinKlinic in London said Kidman, 37, may have had additional surgery to repair cartilage damaged while making "Moulin Rouge" five years ago but it's rare for both knees to go at once.

"I would not be surprised if she has had some sort of plastic surgery," Glancey told the newspaper.

Glancey said she guessed Kidman may have had "lipodissolve, which is a new injection to get rid of fat and is now one of the biggest things in Hollywood." The injection is made from soybeans and is expelled naturally from the body, Glancey said.

Kidman, an avid exerciser, showed off her knees during an early morning swim in recent days with a trainer at the YMCA in Los Angeles.