Less than two weeks after reconstructive right knee surgery in February 2013, Lindsey Vonn already was sounding a positive note, saying she was “really looking forward to Sochi” and defending her Olympic downhill gold medal.

Along the way to the next Winter Games, though, Vonn began facing more setbacks. As she’d move past one, another would surface. In the end, it was too much, even for Vonn, the most accomplished U.S. ski racer in history. Expected to be one of the biggest stars at the upcoming Games, Vonn announced Tuesday — exactly one month before the opening ceremony — she won’t be able to race in Russia.

In a Facebook posting, Vonn said she is “devastated” to miss the Olympics, “but the reality has sunk in that my knee is just too unstable to compete at this level.”

Her personal publicist, Lewis Kay, said in a statement the 29-year-old from Vail, Colo., will have knee surgery again “shortly.”

Like many in her risk-filled sport, Vonn has dealt with injuries often, particularly at major events. She withdrew midway through the 2011 world championships because of a concussion. She raced with a severely bruised shin at the last Olympics. She skipped a race at the 2009 worlds after slicing her thumb open on a champagne bottle. She hurt her knee in training and missed a pair of races at the 2007 worlds. She took a scary fall during training at the 2006 Olympics, then left the hospital to compete.

“She’s come back. She’ll be back,” Vonn’s father, Alan Kildow, said in a telephone interview. “You’ll see a lot of Lindsey Vonn in the future.”

Vonn left the 2010 Vancouver Games with two medals: the first Olympic downhill gold for an American woman, and a bronze in the super-G. She is also a four-time overall World Cup champion, by far the most recognized name in Alpine skiing at the moment — and, as it happens, the girlfriend of Tiger Woods.

Add it all up, and she would have been the focus of plenty of media coverage in Sochi, certainly a main character in NBC’s coverage for a U.S. audience.

“Lindsey gives you great promotional value, and she’s an amazing athlete and an amazing story,” said Gary Zenkel, president of NBC Olympics. “But there are amazing athletes that are going to be in Sochi, many of which we know, some of which we haven’t identified yet.”

To those in the world of skiing, there’s no doubt about the sport’s most important athlete of late.

“Without Lindsey Vonn, the races are just not the same,” Canadian women’s Alpine coach Hugues Ansermoz said last month. “She just attracts so much interest. When Lindsey Vonn is here, there are more people coming to watch the race, there is more interest on TV, more journalists are interested. And her relationship with Tiger Woods makes even more people interested.”

But Vonn has rarely been present on the elite skiing circuit the past 12 months. She tore two ligaments in her right knee and broke a bone in that leg during a high-speed crash at the world championships last February.

As Vonn neared a return, she re-tore her surgically repaired ACL in a crash during training in November. After finishing 40th, 11th and fifth in a trio of World Cup races at Lake Louise, Alberta, in early December, Vonn sprained her MCL during a downhill at Val d’Isere, France, two weeks later.

“I did everything I possibly could to somehow get strong enough to overcome having no ACL,” Vonn said Tuesday via Facebook.

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

Mikaela Shiffrin, the reigning world champion in slalom, and Julia Mancuso, a three-time Olympic medalist, will now draw extra attention as American women trying to reach the Alpine skiing podium in Sochi. Top skiers from other countries who will be favored for medals include Germany’s Maria Hoefl-Riesch, Switzerland’s Lara Gut, Slovenia’s Tina Maze and Liechtenstein’s Tina Weirather.

Shiffrin, the U.S. teenager labeled the “next Vonn” by some, wrote on Twitter that it’s “hard to swallow” that Vonn won’t be competing in Sochi. Another American racer, Stacey Cook, posted on Facebook: “Our team is not the same without you. You leave big shoes to fill.”

After skiing in two downhills and a super-G at Lake Louise last month, Vonn sounded optimistic, declaring she would be in Sochi, “fighting for my medal.”

But shortly thereafter in France — with Woods watching in the finish area — Vonn lost her balance. Her left ski lifted, forcing weight onto her right knee. She grimaced, then clutched that leg.

Kay said Tuesday an MRI “showed an MCL sprain, which coupled with the torn ACL, has made it impossible to stabilize her knee and be ready to safely ski again next month.”

Now Vonn will turn her attention to the 2015 world championships in Colorado. There’s also this: She needs three wins to match the World Cup record of 62 race victories set by Annemarie Moser-Proell of Austria.

“I have every ounce of confidence that Lindsey will be in the starting gate next World Cup season, ready to compete,” said Bill Marolt, the CEO and president of the U.S. Ski and Snowboard Association. “She knows the hard work it takes to get to the top and still has significant goals to achieve in what has been an incredible career.”

U.S. racers captured eight Alpine medals four years ago, their highest total at any Olympics and twice as many as any other country at Vancouver.

That figure may be tough to reach with Vonn sidelined and Bode Miller, who won three medals in 2010, trying to return to form at age 36 after left knee surgery. What’s more, Mancuso has been struggling this season. Off to a poor start in pre-Olympic races, Mancuso recently headed home for a short break.

“We have a strong team that is well prepared. … Now is the time for those athletes to step up,” Marolt said.

Vonn, meanwhile, will go through another operation, another rehab, another road back.

“You need to look at the long run. The problem with the knee is there is not an insignificant risk that you’re going to do more long-term damage that can’t be repaired,” said Kildow, her father. “So have it repaired now. So you can compete in future years. So you can ski and enjoy yourself after you get done competing.”