Two-time Grand Slam winner Li Na has pulled out of three Women's Tennis Association (WTA) tournaments this August, including the U.S. Open, due to knee injury on Thursday.

Li, the World No. 2, will miss the Rogers Cup in Toronto, slated to begin Monday, the Cincinnati Open, which starts the following week, and the U.S. Open at the Flushing Meadows on Aug. 25.

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The 32-year-old Li posted on her Facebook page recently saying that she is withdrawing her participation from the three WTA events due to problems with her knee which she admitted she had since March.

At the recent Wimbledon, Li was eliminated on the third round by Czech Barbora Zahlavova Strycova in straight sets.

"My medical team has advised me that I need to take some time off to rest my knee so it heals," Li said.

Li is the second participant that will miss the events at Toronto and Cincinnati because of an injury. Earlier this week, French Open winner Rafael Nadal also withdrew from the latter WTA tournaments due to a wrist injury he sustained in practice. He, however, expressed intentions of defending his U.S. Open crown if his doctors clear him to play.

Li, who won the Australian Open, was seeded fifth last year at the U.S. Open where she made it up to the semi-finals against Serena Williams who went onto win the Grand Slam crown.

In 2012, Li made it into the finals in Toronto but was defeated by Czech Republic's Petra Kvitova in three sets. At the Cincinnati Open of the same year, Li again went on to the finals against Germany's Angelique Kerber, winning in three sets.

TagsAngelique Kerber, serena williams, rafael nadal