She appeared to have injured her right knee and was treated on the slope for 12 minutes before being airlifted to the hospital.
The injury occurred while the four-time World Cup champion was landing a jump. After losing balance on her right leg, with her knee bending awkwardly, Vonn's ski came off immediately, causing her to go off course and hit a gate before stopping.
The race had already been postponed 3½ hours due to fog and several competitors struggled due to the weather.
"It's not a very difficult course, but in some parts you couldn't see anything," Fabienne Suter of Switzerland said.
Vonn had just returned to racing earlier this year after taking nearly a month off to recover from an intestinal illness.