After Britney Spears tumbled during one of her shows in Las Vegas on Wednesday night the singer assured her fans everything was fine. Well... turns out her injury was worse than she thought.

Spears, 33, who was slated to perform "Piece of Me" shows at Planet Hollywood on Friday and Saturday night, informed her fans late Thursday that the show will not, in fact, go on. "Breaks my heart to share this news," she wrote in an Instagram post. "After hurting my ankle last night my doctor has advised me not to perform this weekend."

The extent of the injury was unknown at press time and a spokesperson for Spears could not be reached for comment.

Britney's been down, but not out before, like the time she had to have knee surgery in 1999 after getting injured in dance rehearsals and again in 2004 when she she hurt her knee during the "Outrageous" video shoot, resulting in the cancellation of her Onyx Hotel Tour.

Here's the video of her fall.