Roger Federer, the former world tennis champion, has pulled out of the French Open, confirming speculation that his recent knee surgeries were causing him pain. He made the decision on Sunday, a day after winning his third-round match. “After discussions with my team, I decided that I should withdraw from the French Open today,” Federer, 39, said in a statement. “After two knee operations and more than a year of rehabilitation, it’s important that I listen to my body and not rush back into competition.”