ZWIESEL, Germany — Three-time World Cup champion Lindsey Vonn sustained a concussion when she crashed during practice and was still unsure Thursday whether she will compete in the final two races before the world championships.

Vonn told The Associated Press she will have a medical check Friday morning before deciding whether to race in a World Cup slalom hours later. A giant slalom was scheduled for Saturday.

“The doctor has to clear me for tomorrow. It depends if I have any symptoms, they are worried about the second impact. Concussions can be pretty dangerous,” Vonn said.

The American hit her head in a crash Wednesday while practicing the giant slalom in Austria. On her Facebook page, Vonn described the “pretty scary crash. … I hit my head pretty hard.”

“I am definitely sore from my crash but I am definitely feeling better as far as my head goes, we’ll play it by ear tomorrow,” she told the AP. “I didn’t ski today just to be safe, to have one more day before the race, try to be a little bit more healthy.”

Vonn said the soreness was “manageable,” and not something that would prevent her from competing at next week’s world championships, where Vonn will defend her super-G and downhill titles in Garmisch-Partenkirchen beginning Tuesday.

“I will definitely be racing at the world championships,” she said. “I crashed or almost crashed many times this season, so it’s not something new. I don’t know what’s got into me this year. It’s been different mistakes every time. Crashing is part of my job, part of ski racing.”

Vonn injured her left knee that required a strenuous recovery after making a major mistake during a downhill in Cortina, Italy, last month.

“It’s not perfect, but it’s definitely better,” Vonn said of her knee. “It’s got to the point where it’s a very manageable injury. It may bother me for a week or two, but I’m happy with it.”

If she is forced to skip the next two races, Vonn could lose more ground to her friend and rival Maria Riesch of Germany in their battle for the overall World Cup title. Riesch holds a 145-point lead over the American.