It's only the second operation for the 38-year-old Federer - the other was on his left knee in 2016 - and one that is certain to raise questions about his future in tennis.
He posted on social media Thursday that his knee had been an issue "for a little while."
"I hoped it would go away," he said.
The man who has spent more weeks ranked No 1 than any other and owns a men's-record 20 grand slam titles said the operation was in his home country of Switzerland on Wednesday. He currently is ranked No 3 behind rivals Novak Djokovic and Rafael Nadal.
