Roger Federer, winner of 20 Grand Slam titles, has announced his retirement from tennis at the age of 41 after a string of injuries. Federer posted an audio message on social media on Thursday afternoon explaining his 'bittersweet' decision. 'As many of you know, the past three years have presented me with challenges in the form of injuries and surgeries,' he said. 'I’ve worked hard to return to full competitive form. But I also know my body’s capacity and limits, and its message to me lately had been clear.' 📷 Anne-Christine Poujoulat/AFP