WASHINGTON — Olympic downhill champion Lindsey Vonn has undergone successful surgery to repair the injured right knee that cost her a chance of defending the title she won in Vancouver four years ago, the American announced Wednesday. Vonn, who has battled knee ailments over the past year, was forced to withdraw from next month's Sochi Games in Russia to have the operation, although she is expected to make a full recovery in time for the 2014-15 World Cup season. The 29-year-old four-time World Cup champion, one of the biggest attractions in winter sport, spoke of the surgery via her Facebook account. “Resting with loved ones,” Vonn wrote. — Reuters