Lindsey Vonn won't be able to defend her 2010 Olympics gold medal in downhill skiing at next month's Winter Olympics in Sochi because of a lingering knee injury.

Vonn took to her Facebook page to make the announcement official.

"I am devastated to announce that I will not be able to compete in Sochi," Vonn wrote on her Facebook page. "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."

Vonn tore her ACL and MCL in her knee last February, then partially tore the same ligament again during a training run in November.

On Dec. 21 in Val d' Isere, France, Vonn suffered more damage to the knee when an MRI revealed an MCL sprain.

"Coupled with the torn ACL, it has made it impossible to stabilize her knee and be ready to safely ski again next month," a statement from Vonn's publicist read.

Vonn, who is also the girlfriend of Tiger Woods, is the most successful female Alpine skier in American history. She has won 17 World Cup titles, including a record six-straight downhill crowns. She is the only female American skier who has won a gold medal in the downhill at the Winter Olympics.

She has 59 World Cup wins, three short of the all-time record set by Austria's Annemarie Moser Proell.

Vonn also announced that she will have surgery on the knee soon.

"I'm having surgery soon so that I can be ready for the World Championships at home in Vail next February," Vonn wrote. "On a positive note, this means there will be an additional spot so that one of my teammates can go for gold."