Peta Murgatroyd Peta Murgatroyd

Peta Murgatroyd will not be participating in Season 21 of Dancing with the Stars.

The Aussie pro has a severe ankle injury that requires surgery, and doctors estimate it will take her six to eight weeks to recover, she tells People.

Murgatroyd, 29, spent the summer participating in the Dancing with the Stars live tour, but said she noticed "something was not right" when she began rehearsing with her new partner, singer Andy Grammer. She had an MRI, which showed that she had four torn ligaments in her ankle as well as a floating piece of bone. Her surgery is scheduled for mid-September.

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"It was a really bad diagnosis," she tells People. "My doctor said I needed surgery and I knew I needed to put my health first if I want to keep dancing on the show into my 30s. ... I'm so in love with the show and I'm a very competitive person. It's really sad."

Grammer's new partner will be announced, along with the rest of the Dancing cast, on Good Morning America Wednesday. Murgatroyd says she hopes to return to the show in Week 8 or 9 to coach Grammer in the rehearsal room and help with choreography.

"It was awful telling Andy. He had specifically asked to be partnered with me and I felt like I was letting him down," she tells People. "But he understood and has been a great guy about it."

Murgatroyd, who won Season 14 of Dancing with partner Donald Driver, shared the news with her fans on Twitter Monday night, calling the news "heartbreaking."

Dancing with the Stars returns Monday, Sept. 14 at 8/7c on ABC. Are you sad Peta won't be on Season 21?

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