Berlin: Germany's rising tennis star Andrea Petkovic says she has no idea when she will be able to return to normal training as the stress fracture of her lower back is taking time to heal.

The 24-year-old, who reached the quarter-finals of the US, French and Australian Opens in 2011, had an MRI scan on Monday with renowned German doctor Hans-Wilhelm Mueller-Wohlfahrt, but there was no good news.

"Everything is the same, I'm still in rehab," she told SID, an AFP subsidiary, having withdrawn from the Australian Open in January because of the stress fracture which has plagued for for several months.

"In 14 days, I will go for another check-up."

In a bid to help the injury heal quicker, the world number ten, from Darmstadt near Frankfurt, has been living in a hotel for the last two weeks to work with her rehab physiotherapist who lives on the other side of Germany.

"I train for about five to six hours a day. I do stabilisation exercises for the back and torso and also for the knees," said Petkovic.