Injured Petkovic out of Australian Open

Germany's top-ranked tennis player Andrea Petkovic has pulled out of next week's Australian Open Grand Slam tournament with a stress fracture, she said on Wednesday.

"Sorry to announce that I had to withdraw from the Australian Open with a lower back stress fracture," the 24-year-old said in a post on her Twitter account. "Going back home, will miss my Aussie fans!"

The world number 10 suffered a knee injury in October, but returned to play her first WTA tournament at Brisbane last week where she made the quarterfinals.

She was dumped out of the Sydney International in the second round on Tuesday by Pole Agnieszka Radwanska in straight sets.

Bosnia-born Petkovic, famous on tour for her post-match victory dances, upset Maria Sharapova on the way to the quarterfinals at Melbourne Park last year where she was stopped by eventual finalist Li Na.  The 10th seed's withdrawal came shortly after seven-times Grand Slam winner Venus Williams pulled out, also citing health reasons.

Williams has been receiving treatment for Sjogren's syndrome, an auto-immune disease that causes fatigue and joint soreness.

A number of other contenders in the women's draw head into the year's first Grand Slam under injury clouds.