'Recurring' knee problem forces two-time Grand Slam winner Li Na to retire

China's two-time Grand Slam champion Li Na has announced her retirement from tennis, due to a knee injury.

Na posted the news on her Facebook page on Friday, citing a recurring knee problem. She wrote that she has succeeded on the global stage in a sport that a few years ago was in its infancy in China.

Na, who won the Australian Open this year to add to her 2011 French Open title, also stated that what she has accomplished for herself is beyond her wildest dreams, adding that what she accomplished for her country is one of her most proud achievements, Stuff.co.nz reported.

Na became the first player from China to win a grand slam singles title by winning the 2011 French Open, and clinched the Australian Open title in January in her third trip to the final at Melbourne Park.

Na, who has won nine WTA singles titles to date, only entered seven tournaments after that, and hasn't played since a third-round defeat at Wimbledon. She withdrew from three tournaments in August, including the US Open, citing a right knee injury, the report added.