Serena Williams is withdrawing from Wimbledon doubles competition after injuring her knee at the tournament earlier this week.The injury occurred on Wednesday, while Williams was playing in the singles competition. At the time, her agent said she intended to play doubles with sister Venus Williams as her partner.Serena Williams announced her withdrawal in an Instagram post that included photos and videos of the injury.“I’m heartbroken to have to withdraw from doubles. Coming back to compete again has been a gift, and the opportunity to play alongside @venuswilliams once more meant the world to me,” she wrote. “I did everything I could to be ready, but unfortunately my knee just isn’t ready to compete.”The post included video of Williams appearing to limp down a hallway with her right knee in bandages and four syringes filled with yellow fluid the tennis champion said was drained from her knee.“The good news is my knee shouldn’t swell or collect that much fluid again,” she wrote. “The bad news is that, as hard as I tried, I just wasn’t able to get it ready for doubles.”Williams also thanked the tournament’s director for giving her the opportunity to play, and her fans.“All I can say is stay tuned to a city near you,” she said.