Austria's ski federation president said doctors told him that Vonn tore her cruciate and lateral ligaments. Peter Schroecksnadel added that this is "the only injury she has, nothing besides this."
The U.S. team gave no immediate update on Vonn's condition but said it would release a statement later in the day.
This is the sixth straight major championship in which Vonn has been hit with injuries. This crash comes almost exactly one year before the start of the 2014 Winter Olympics in Sochi, Russia.
The four-time overall World Cup champion lost balance on her right leg while landing after a jump. Her ski came off immediately, and she slid off course and hit a gate before coming to a halt. She was treated on the slope for 12 minutes before being going to the hospital.
Vonn returned to the circuit last month after an almost monthlong break from racing to fully recover from an intestinal illness that put her in a hospital for two days in November.
Vonn trailed race winner Tina Maze of Slovenia by 0.12 seconds shortly before the crash.
The race, which was postponed for 3½ hours because of fog, resumed after another 15-minute delay. Several racers struggled with the conditions.
"It's not a very difficult course but in some parts you couldn't see anything," Fabienne Suter of Switzerland said.
Vonn is building a long list of medical mishaps. Two years ago, she pulled out midway through the last worlds in Garmisch-Partenkirchen, Germany, because of a mild concussion. At the 2010 Vancouver Olympics, Vonn skied despite a severely bruised shin to win the downhill and take bronze in the super-G.
At the 2009 worlds in Val d'Isere, France, she sliced her thumb on a champagne bottle after sweeping gold in the downhill and super-G, forcing her out of the giant slalom. At the 2007 worlds in Are, Sweden, Vonn injured her knee in training and missed her final two events.
And at the 2006 Turin Olympics, she had a horrific crash during downhill training and went directly from her hospital room to the mountain to compete in four of her five events.