Veteran actress Sally Field had to undergo surgery on her knee after gaining nearly two stone (12 kilograms) for her Oscar-nominated turn in Lincoln.

The 66-year-old star played First Lady Mary Todd Lincoln opposite Daniel Day-Lewis as U.S. President Abraham Lincoln in Steven Spielberg's historical drama, and she piled on the pounds in a bid to look more like her character.

Field admits it took her a year to lose the weight after filming wrapped, and she also had to undergo surgery on a knee injury she sustained due to her heavier frame.

She says, "I began to work out like a mad fiend (after filming finished). I had two trainers. I really worked out hard four times a week. I eventually had to have knee surgery. My little frame couldn't hold this amount of weight."