Lady Gaga has been forced to postpone four dates on the US leg of her Born This Way Ball tour.
The 26-year old took to Twitter yesterday (February 12) to make the announcement, after suffering from synovitis - which is inflammation of the joints.
She's had to cancel two concerts in Chicago, as well as shows in Detroit and Hamilton.
Gaga said: "Im so sorry. I barely know what to say. I've been hiding a show injury and chronic pain for sometime now, over the past month it has worsened. I've been praying it would heal.
"I hid it from my staff, I didn't want to disappoint my amazing fans. However after last nights performance I could not walk and still can't."
She continued: "To the fans in Chicago Detroit & Hamilton I hope you can forgive me, as it is nearly impossible for me to forgive myself. Im devasted & sad (sic).
"It will hopefully heal as soon as possible, I hate this. I hate this so much. I love you and Im sorry."
Lady G is expected to return to the stage for a two-night stint in Philadelphia on February 19-20, with the rescheduled dates due to be announced later.