Henin-Hardenne, the 2004 champion in both Sydney and Melbourne, has a micro fracture of the femural condyle in her right knee (bone on the outside of the right knee), which she incurred on December 28 while practicing in Florida.

The small fracture was confirmed in an MRI scan in Sydney on Saturday. Henin-Hardenne has been recommended to rest for 4-6 weeks.

"I started to have pain in the knee nearly two weeks ago, and it started to get worse over the next few days," said Henin-Hardenne. "When I came to Australia I stopped training for four days, hoping it would get better, but it didn't.

"I'm so disappointed that I'm not going to be able to play in Australia and defend my titles. I was feeling fit and really ready to play after all my problems last year. But because I haven't trained very much recently, I realised there is the risk of injury in the next few months." Henin-Hardenne was restricted to nine tournaments in 2004 as she was sidelined by a viral illness.

"Right now I know I need to take care of myself and make sure I'm fully fit. This injury is probably harder to accept than what happened to me last year because everything else is fine and I felt my tennis was improving. I was really looking forward to playing in Australia. I love playing here."