(Reuters) - U.S. Open champion Stan Wawrinka will not defend his title in New York later this month and will also miss the rest of the season due to a knee injury, the Swiss said on Friday.
The 32-year-old battled with the injury throughout the grasscourt season and was knocked out in the first round at Queen's and at Wimbledon.
"I am sad to announce that after talking with my team and doctor I had to make a difficult decision to undergo a medical intervention on my knee," Wawrinka posted on Facebook.
"This was the only solution to make sure I will be able to compete at the top level for many more years.
"I also want to take this opportunity to thank my fans for sending plenty of messages of support during the last couple of days. I will see you all in 2018!"
The world number four had already announced on Wednesday that he was withdrawing from the Rogers Cup, that begins Monday in Montreal and the Western & Southern Open in Cincinnati due to injury.
Wawrinka joins world number five Novak Djokovic on the sidelines, with the Serb also missing the rest of the season due to an elbow injury.
World number one Andy Murray, who is struggling with a hip problem, is also a major doubt ahead of the final grand slam of the calendar year, which begins on Aug. 28 at Flushing Meadows. The Briton withdrew from the Rogers Cup on Thursday.
Reporting by Hardik Vyas in Bengaluru and Steve Keating in Toronto; Editing by Toby Davis