Lindsey Vonn, the defending Gold Medalist in women's downhill, pulled out of the Sochi Olympics on Tuesday morning because of a lingering knee injury. 

Vonn made it official on NBC's Today Show, and followed up with a statement on her Facebook page. "I did everything I possibly could to somehow get strong enough to overcome [a recent ACL injury] but the reality has sunk in that my knee is just too unstable to compete at this level," Vonn said in her announcement.

If healthy, Vonn would be one of the biggest stars on the U.S. Olympics squad, but an injury-plagued season has forced her to the sidelines for much of 2013. Vonn underwent surgery to reconstruct two knee ligaments last February. She then injured the same knee twice more, once in November and again in late December

Her coaches thought a small chance existed that she could compete at Sochi, and were ready to take her even though Vonn hasn't skied in weeks. But Vonn has decided to undergo knee surgery, again, in order to compete at the FIS 2015 World Championships in Vail, Colorado, leaving the door open for a healthier competitor to take her place. 

Vonn is only American woman ever to win gold in the Olympic downhill. Here is Vonn's full statement:

I am devastated to announce that I will not be able to compete in Sochi. I did everything I possibly could to somehow get strong enough to overcome having no ACL but the reality has sunk in that my knee is just too unstable to compete at this level. I'm having surgery soon so that I can be ready for the World Championships at home in Vail next February. On a positive note, this means there will be an additional spot so that one of my teammates can go for gold. Thank you all so much for all of the love and support. I will be cheering for all of the Olympians and especially team USA!