Lady Gaga has been forced to postpone four shows on her current tour because of an injury that left her unable to walk.
Suffering from synovitis, a severe joint inflammation, performances set in Chicago, Detroit and Hamilton, have been postponed.
Speaking on Twitter, the pop star said she had injured herself during a performance some time ago, and the condition had worsened.
She said she was immobile following Monday's concert in Montreal, Canada, and had been hiding her injury from her staff.
The singer apologised to her fans, saying "I love you and I'm sorry", she added "I'm devastated and sad".
The rest of the Born This Way Ball tour is expected to continue on schedule, beginning with a two-night stand in Philadelphia on February 19 and 20.
Dates for the missed shows will be announced at a later date.
List of the missed shows:
- February 13th and 14th: Chicago
- February 16th: Detroit
- February 17th: Hamilton, Ontario, Canada