American skier Lindsey Vonn revealed Wednesday morning on the "Today" show that she has a shin injury that could affect her participation and performance in the Winter Olympics, which begin Friday.

Vonn said her shin bruise is extremely painful because it is located at a point of contact with her ski boot. She could not give "Today" show host Matt Lauer an estimate -- in terms of percentage -- of how healthy she was entereing the Games.

Vonn said she injured her right shin in a training run a week ago. It was diagnosed, she said, as a deep muscle bruise.

Vonn is widely regarded as the top American in the Games. She was planning to compete in all five Alpine skiing disciplines at Vancouver. The first, the women's super combined, is scheduled for Sunday.

"I honestly don't know if I'll be able to do it," Vonn said.