Roger Federer has said he will miss a number of tournaments, including the French Open in May, after a knee surgery in Switzerland on Wednesday.

The 20-time Grand Slam champion had been struggling with injury at the Australian Open, where he made a semi-final exit to eventual champion Novak Djokovic, and has not played since.

Federer, 38, said he would also miss the ATP tournaments in Dubai, Indian Wells, Bogota and Miami.

“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 arthroscopic surgery in Switzerland yesterday,” Federer said in a statement on Twitter on Thursday.

“After the procedure, the doctors confirmed that it was the right thing to have done and are very confident of a full recovery.”

Last year, the Swiss legend played only two tournaments on the claycourt before arriving in Paris for the French Open. His agent had said last week that Federer was planning on playing only at Roland Garros. The French Open begins on May 24.