Niall Horan has confirmed reports that he has undergone knee surgery.

However, the One Direction man admitted the operation was "much larger" in scale that initially thought.

The singer, who has had knee trouble in the past, was pictured on crutches after apparently having surgery in the US.

He took to Twitter today (January 17) to confirm the reports, but he added that he would like some privacy as he recovers.

Horan said: "Hey guys I know most of you have seen those pics today! Yes I've had major knee surgery, a much larger surgery than first anticipated.

"But i would like to tell u, it was a complete success! Considering the scale of it! So all I ask of you guys is that you would respect my privacy as I try to recover and get for the where we are tour!"

Horan added that he effectively misled fans about his whereabouts in an effort to secure privacy. When asked if he "lied" about being in the UK, the singer said: "I did! As It was a very important time for me ,and I didn't want to have fans knowing my whereabouts. Needed privacy."

One Direction meanwhile are due to head out on their Where We Are world stadium tour from April.