Serena says she's rarin' to go

World No 1 Serena Williams insists she is fit and ready for a shot at her seventh Australian Open title beginning next week, downplaying a knee injury that forced her out of the Hopman Cup.

Serena retired due to soreness in her left knee during a singles match on Jan 6 at the mixed-team tournament in Perth, casting doubt over her ability to defend her title at the opening Grand Slam of the season.

But the 34-year-old told the Melbourne Herald Sun she is ready.