Vonn, 29, has had a series of injuries since a crash last Feb. 5 that resulted in a broken tibia and torn anterior cruciate ligament in her right knee. She reinjured the knee in a race Nov. 20, partially retearing the ACL.
She raced Dec. 6 and said she planned to cut back on her schedule to be healthy for the Olympics, which begin Feb. 7 in Sochi, Russia.
But Tuesday she posted a tweet saying she was "devastated to announce that I will not be competing in Sochi."
She expanded her comments on her Facebook page, stating, "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 said she expected to have surgery soon "so that I can be ready for the World Championships at home in Vail next February."
She ended the post with: "I will be cheering for all the Olympians and especially team USA! XO Lindsey."
Vonn, in addition to winning the downhill Olympic gold, won overall World Championships in 2008-10 and 2012 and World Cup discipline golds in the super-giant slalom (2009-12), downhill (2008-13) and the combined (2010-12).