One Direction's Niall Horan recovering from knee surgery

One Direction's Niall Horan took to Twitter Friday to confirm recent knee surgery, which he said turned out to be more serious than he expected.

Horan tore some ligaments in the knee in December.

When U.K. newspaper The Sun published a picture of the singer on crutches at London's Heathrow Airport, Horan posted an explanation to his nearly 17 million Twitter followers .

"Yes I've had major knee surgery, a much larger surgery than first anticipated," Horan tweeted. "But i would like to tell u, it was a complete success! Considering the scale of it!"

Horan will have a few months to recuperate before going back out on the road. One Direction is slated to start a South American tour in late April. The group will play stadiums in the U.S. this summer,
starting Aug. 4 at New Jersey's MetLife Stadium.

Get better soon Niall