Lady Gaga postpones US concerts after joint injury
Lady Gaga has postponed her world tour after sustaining an injury which she says has left her unable to walk.
The singer has severe inflammation of the joints, known as synovitis.
Writing on Twitter, Gaga apologised to fans, saying she was "devastated" at having to delay several shows in America and Canada.
"I've been hiding a show injury and chronic pain for sometime now," she wrote. "However, after last night's performance, I could not walk."
"To the fans in Chicago, Detroit & Hamilton. I hope you can forgive me, as it is nearly impossible for me to forgive myself. I'm devastated & sad," she tweeted.
"It will hopefully heal as soon as possible, I hate this. I hate this so much. I love you and I'm sorry."
Performances on 13 and 14 February in Chicago and 16 February in Detroit will now be rescheduled. She has also postponed a concert in Canada on 17 February in Hamilton, Ontario.
The new dates for these shows are yet to be announced.
It is thought the pop star will be well enough to perform again in Philadelphia on 19 February.