Lady Gaga thought about her fans' "pain and perseverance" as she went into surgery yesterday.

The American singer has cancelled the final 21 dates of her Born This Way Ball tour after sustaining synovitis - a severe inflammation of joints - and a tear in her right hip.

Yesterday she informed her Twitter followers she was about to have an operation on her hip and she has now reassured them she is recovering well.

"As they wheeled me into surgery today, I thought about all of your pain and perseverance, your unique family situations, school environments, health issues, homelessness, identity struggles - sometimes you are so brave that it terrifies me. I wonder how it's even possible," she wrote on her blog.

Although it was thought Gaga would need to have surgery to ease her ailment, the actual operation date was decided very quickly.

She has thanked her fans, who she called her Little Monsters, for giving her "a lot of strength" as she received treatment. The star explained thinking about their stories was what helped her through and made her realise she is lucky to be in her situation, even though she is ill.

"I thought to myself, I'm alive, I'm living my dream, and this is just a bump in the road. I'm grateful because this is temporary, and for some it is not," she wrote. "You have changed my life. I love you and am proud to be a part of your lives. If you can do it, I can do it too, and if we stick together we can get through anything."

Gaga cancelled the first tour date last week, before announcing she was unable to take to perform at any of the scheduled shows.

She apologised to her fans, explaining she suffered the injury some time ago but had been attempting to cover it up to avoid disappointing them.

Earlier this week she tweeted a picture of her wheelchair, which she has named Emma.