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Lady Gaga has now cancelled all of her Born This Way Ball tour to undergo hip surgery.

Tour promoter Live Nation has released a statement to say the singer's injuries are more serious than originally thought.

Earlier this week, it was announced she was suffering from inflammation of the joints called synovitis.

At first the 26-year-old just cancelled four US gigs but has now been forced to cancel the remainder of her tour.

"After additional tests to review the severity of the issue, it has been determined that Lady Gaga has a labral tear of the right hip," Live Nation said.

"She will need surgery to repair the problem, followed by strict downtime to recover.

"This, unfortunately, will force her to cancel the tour so she can heal," it added.

Live Nation said ticket holders would have their money refunded.

After cancelling the initial gigs, Lady 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.