( CNN ) -- World No . 3 Rafael Nadal has been forced to withdraw from the U.S. Open due to an ongoing knee complaint , the Spanish tennis star announced on Wednesday . The French Open champion has a history of knee problems , and has not played since a surprise second-round defeat at Wimbledon in June . The former world number one was unable to defend his Olympic title in London , and the the 26-year-old had to pull out of last week 's tournament in Toronto as well as this week 's event in Cincinnati . `` I am very sad to announce that I am still not ready to play and have to withdraw from this year 's U.S. Open in NYC , '' Nadal told the U.S. Open website ahead of the season 's final grand slam , which runs from August 27-September 9 . `` I am sorry since I always found great crowds and great support , but I have to continue with my recuperation and preparation to be ready to play in the right conditions . '' Nadal , who was beaten in last year 's final by Novak Djokovic , missed large spells of the 2007 season due to knee problems and had to withdraw from the 2008 end-of-season championship plus the Davis Cup final due to similar troubles . In 2009 , Nadal was unable to defend his Wimbledon title after he was diagnosed with tendinitis in both knees , and he has occasionally missed tournaments since to try to manage the problem . In March this year , he was forced to withdraw before his semifinal at the Miami Masters tournament due to the injury . However , he managed to play a full clay-court season , winning three titles before clinching a record seventh French Open at Roland Garros . Nadal then lost in the quarterfinals of the Halle grass event in Germany , and was beaten at Wimbledon by 100th-ranked Czech Lukas Rosol .
Last year 's runner-up Rafael Nadal withdraws from the U.S. Open . Spanish player has already missed Olympics and North American events . Nadal lost to Novak Djokovic in last year 's final in New York . Former world number one has a history of knee problems .