Lady Gaga is undergoing an operation.

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"Emma." Picture: @ladygaga/Twitter

Lady Gaga is undergoing an operation.

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

It was suspected she may need surgery and the star has announced she is now in hospital.

"Going in for surgery now. Thank you so much for sending me love and support. I will be dreaming of you," she wrote on Twitter.

Earlier this week the star hinted at the severe nature of her ailment. She posted a message on Twitter introducing her fans to her new friend "Emma", along with a picture of her wheelchair.

Gaga cancelled the final 21 dates of her tour last week and told fans she was devastated to have to do so.

She penned an emotional message to them on the social networking website in which she spoke about the chronic pain she's been in.

"I've been hiding a show injury and chronic pain for some time now. Over the past month it has worsened," she wrote.

"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 night's performance, I could not walk and still can't.

"I'm devastated and sad. It will hopefully heal as soon as possible, I hate this. I hate this so much. I love you and I'm sorry."