US Ski Team spokesman Tom Kelly said Vonn was not admitted to hospital and was being evaluated in nearby Vail, Colorado, by the same doctor who repaired her right knee in February.
"We expect to have clarity on the situation in the next 24 hours," Kelly told Reuters without providing any other details.
Four-time overall World Cup champion Vonn was due to begin official downhill training for next week's World Cup races scheduled at Beaver Creek.
The 29-year-old American tore ligaments in her right knee last February in a crash racing super-G at the world alpine championships in Schladming, Austria.
The women's downhill, super-G and giant slalom are being contested at Beaver Creek from November 29-December 1.
Vonn, who has been wearing a protective knee brace as she rounds back into shape, was aiming for a return to top form in time for the February 7-23 Sochi Olympics.
The champion skier, who lives in Vail, had been saying she was eager to return to competition and was at Sunday's National Football League game in Denver between the Broncos and Kansas City Chiefs along with her boyfriend Tiger Woods.
USA; American golfer Tiger Woods with girlfriend American skier Lindsey Vonn on the sidelines before the game between the Kansas City Chiefs against the Denver Broncos in the first quarter at Sports Authority Field at Mile High.
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