According to the New York Times, one of her skis flew off as she tumbles down the hill. Vonn tore two knee ligaments from the accident.
You can see her leg actually bend backwards as she lands in the clip right before she falls down. Although severe, she is expected to return to the sport in time for the 2014 Olympics in Sochi Russia. However, the United States ski team has announced that she will be missing the rest of the ski season.
According to U.S. Ski Team Medical Director Kyle Wilkens, Vonn suffered a torn ACL and MCL in her right knee and a lateral tibial plateau fracture. She will be out for the remainder of this season but is expected to return to racing for the 2013-14 Audi FIS World Cup season and the 2014 Olympic Winter Games in Sochi.
Lindsey Vonn is a world-renowned professional skier that has won 4 world championships and 2 Olympic medals for the US team. Vonn recently divorced her husband of 5 years, Thomas Vonn, in January of this year.
A video of the accident can be seen below.
Video of accident is at this domain