PARIS — Australian Open runner-up Jo-Wilfried Tsonga withdrew from the French Open today because of an injured right knee and will have surgery next week.

Tsonga said his injury occurred before he pulled out of France's Davis Cup quarterfinal loss to the United States in April.

"Since then it was a test to see whether it would hold up," said Tsonga, who withdrew from his semifinal in Morocco on Friday. "I reached the critical time when I needed an operation before it's too late."

Nicolas Kiefer of Germany and Fabio Fognini of Italy also were out a day before the clay-court major begins.

Tsonga, who was seeded 14th, has been bothered by his knee for about a month. He said he will need three to four months to recover.

Tsonga will be replaced in the draw by Luis Horna of Peru. Also joining the main field are Marc Lopez of Spain and Josselin Ouanna of France. Lopez will face 26th-seeded Jarkko Nieminen of Finland in the first round, and Ouanna will play Juan Martin Del Potro of Argentina. Horna plays Scoville Jenkins of the U.S.

Tsonga surprisingly reached the Australian Open final this year, beating Rafael Nadal in the semifinals before losing to Novak Djokovic.

"It's enormously frustrating," he said. "To play very well in any Grand Slam is super, but to play very well at Roland Garros would have been magic."

Kiefer, who also missed the French Open last year because of injury but reached the fourth round in 2005, withdrew because of a sore throat. The 38th-ranked German's best result at a Grand Slam tournament came at the 2006 Australian Open, where he reached the semifinals but lost to eventual champion Roger Federer.

Fognini, ranked 87th, made his Grand Slam debut at last year's French Open and lost in the first round.