01/17/2014 10:49 am ET Updated Jan 25, 2014

One Direction's Niall Horan Has 'Major Knee Surgery' 3 Months Before Tour

Jordan Strauss/Invision/AP

Niall Horan, one-fifth of the hugely successful boy band One Direction, has had "major" knee surgery just three months before the group is set to go on tour.

British tabloid The Sun published a photo of Horan walking on crutches, which sparked a fury of speculation and concern among the band's hardcore tween fan base. The 20-year-old took to Twitter, offering an explanation to his 16.7 million followers:

One Direction's "Where We Are" tour kicks off April 25 at Estadio El Campin in Bogota, Colombia, reports E! News.