Out in Australia

THE ASSOCIATED PRESS

MELBOURNE, Australia -- Andrea Petkovic has withdrawn from the Australian Open with a stress fracture in her lower back.

Petkovic, ranked No. 10, lost 7-5, 6-4 to Agnieszka Radwanska of Poland in a second-round match at the Sydney International on Tuesday. She needed an injury timeout during the match to receive treatment from a trainer.

The 24-year-old Petkovic was seeded 10th at the Australian Open, which begins Monday at Melbourne Park.

The German is known for her celebratory dance after she wins -- a hip-shaking wiggle that has pleased tennis fans but often irritated her opponents.

She is coming off her best year in 2011, advancing to the quarter-finals of the Australian Open, French Open and U.S. Open and the third round of Wimbledon.