Beijing, Sep 19 (IANS) China's first and only Grand Slam winner Li Na formally announced her retirement from tennis Friday.

Li, 32, made the announcement on her microblog, the Chinese equivalent to Twitter, a day after rumours about her leaving had already spread all over internet and social media, reports Xinhua.

Li called 2014 "one of the most important years" in her life, as well as a "difficult one".

"I have experienced things that I have to stand up to, including making a decision to end my tennis career," Li wrote in her microblog.

Experiencing ups and downs in 2012 and 2013, Li found the top of her game again this year, bagging a second Grand Slam title in the Australian Open.

"As a professional, it is the right decision to step away from the tennis court now," said the Wuhan native, whose hometown is holding the first WTA event that started Friday.

Li's retirement came as a surprise but an understandable decision. Speculation has been rife since she pulled out of the US Open and other hard-court tournaments because of knee injuries that flared up in July.

Her husband Jiang Shan revealed Friday that Li is currently receiving treatment on both her knees in Germany.