The race itself was later called off due to bad weather.
Vonn, the finest woman skier of her generation, was treated for nearly one hour following Saturday's race on the same course after suffering what she described as an "acute facet (spinal joint) dysfunction."
She said her back "seized up" near the sixth gate and, although she completed the course, she crumpled after the finish line and was clearly in enormous pain.
"Unfortunately I will not be able to race today," she said on Twitter.
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"I am extremely disappointed but my biggest goal this season is the Olympics and I need to take care of myself now so I can be ready for next week, and more importantly, for February."
(Writing by Brian Homewood in Berne; Editing by Toby Davis)
