Roger Federer ruled out of French Open after undergoing surgery on knee injury

Roger Federer hopes to return in time for the grass-court season after undergoing surgery on a knee injury which has been giving him trouble for "a little while".

The 20-time Grand Slam champion reached the semi-final of the Australian Open last month before losing to eventual champion Novak Djokovic.

Federer, who has previously opted out of the French Open to pepare himself for the grass, has this year been forced off the clay courts as he recovers from surgery ahead of another crack at Wimbledon.

Federer, 38, wrote on Twitter: "My right knee has been bothering me for a little while.

"I hoped it would go away but after an examination, and discussion with my team, I decided to have an arthroscopic surgery in Switzerland yesterday."

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