Organisers cancelled the race in worsening conditions with snow falling, and Vonn, leader of the downhill standings, was the sixth and last of those out of the start hut.
"I crashed today in the Downhill race in Switzerland and injured my left knee," Vonn said on social media just days before the start of the Winter Olympics in Italy.
"I am discussing the situation with my doctors and team and will continue to undergo further exams. This is a very difficult outcome a week before the Olympics... but if there is one thing I know how to do, it's a comeback."
The Olympics kick off on February 6th with the opening ceremony in Milan's San Siro stadium.
"My Olympic dream is not over. Thank you for all the love and support. It's not over until it's over," Vonn said.
The 41-year-old, in winning form as she prepares for an age-defying Olympic comeback next week, lost her balance on Friday and crashed into the side netting, with her airbag inflating.
She was able to get back up on her skis but was seemingly in pain from her left leg, stopping at one point to clutch her knee.
"She has some pain, so it's better to have some checks. The physio did some checks, they seemed OK, but there were things he was not 100% sure so it was good to have it checked (at the hospital)," two-time Olympic champion Aksel Lund Svindal, Vonn's coach this season, told Reuters.
She was comforted at the finish by teammate Jacqueline Wiles.
Three of the first six skiers down the piste, shortened due to weather conditions with snow falling steadily, crashed.
Vonn had bib number six as the first of the seeded racers at Crans-Montana in Switzerland, where 40 people died in a fire in a bar on New Year's Eve, making the race an emotional World Cup leg.
Austrian Nina Ortlieb was able to ski away, but Norway's Marte Monsen was less fortunate.
Clutching her knees after being freed from the netting, Monsen was strapped into a stretcher and carried away with a bloodied face.
"Sending my best to Marte, who also had a major crash and injury today," Vonn said.
Italy's Federica Brignone, who returned to racing earlier this month after more than nine months out of action following serious leg injuries, was on the starting list with bib 16.
Svindal said going ahead with the race in the morning was a tough decision for the organisers, before underlining the dangers of the course.
"To start, the race seemed like OK, but this hill has a very small margin for error, meaning if the speed is a little bit higher, it goes from quite easy to very dangerous. If you look at the jumps, it's very short landings, so you can jump 30 metres, but if you jump 35, you're finished," he said.
The first training run for the women's Olympic downhill is scheduled for Wednesday.
Any injury at this late point, with the downhill scheduled for February 8 and little time for recovery, will be a major concern.
Speed queen Vonn has been billed as one of the standout stars of the Games, and she and teammate Mikaela Shiffrin are the two most successful female skiers in World Cup history with a combined 192 wins between them.
Vonn, the 2010 Olympic champion, has been on the podium five times in five downhills this season prior to Friday, with two wins, a second place and two thirds.
The four-time overall World Cup champion, with 84 wins, returned in 2024 after nearly six years out and following successful knee surgery.
"I'm physically in possibly the best shape I've ever been in, which is fun, and my body doesn't hurt. So I think that's the best part of all," she said last month.