The Italian earned the nickname 'Winnerhofer' after bagging three medals, including the Super-G gold, at the Garmish-Partenkirchen world championships in 2011, but since then, wins had been fewer than health problems.
A 2011 injury during training left him with a concussion and back problems and a car crash in July revived painful memories.
"This podium is very important for me because some time ago I wasn't even sure I would be able to keep skiing. Today, I beat Svindal, I couldn't be happier. It's more than a race today, it's a recovery," said Innerhofer.
His victory in last winter's final Super-G in Schladming had signalled his talent was intact and the Italian, 28, confirmed his return to form on the Birds of Prey piste in one minute and 41.69 seconds to win his second World Cup downhill.
Innerhofer, who clinched his maiden downhill victory in Bormio in 2009, beat pre-race favourite Aksel Lund Svindal by 0.23 seconds while fellow Norwegian Kjetil Janrsrud was third, 0.50 behind.
"It's been such a long time since my first downhill victory in Bormio that I don't really know what to say, especially after what I've been through," said Innerhofer, who has now won four World Cup races.
"I really didn't know what to expect. I went through hell for the past 10 months and it doesn't seem real. After each skier I kept looking at the scoreboard to make sure I was still up there."
Svindal, who achieved a rare double by winning both the downhill and the Super-G in Lake Louise a week ago, failed to make it three in a row but took his lead in the overall World Cup standings to 110 points over giant slalom world champion Ted Ligety of the U.S.
On a roll after his two victories in Canada, the Norwegian admitted he had probably taken too many risks on a piste he knows like the palm of his hand.
"It's clear that I was going too fast. To be forced to brake in a downhill is just crazy. It cost me victory but I took my chances and that's the way to do it on a piste like this," he said.
To share the podium with team mate Jansrud was ample consolation.
"I'm glad to be on the podium with Kjetil. As I said before, you can never rule him out, in downhills and Super-G's as well.
"I'm looking forward to tomorrow as I'm sure there's more to come for Norway during the weekend," Svindal added.
The Beaver Creek programme continues with a Super-G on Saturday and a giant slalom on Sunday.
The race was marred by the crash of Germany's Tobias Stechert, who ended his run in the safety nets with a knee injury.
"I hurt my knee. Unfortunately I had this before and I know what it is to tear your ligaments. I hope that's not the case but I feel it's not good," he said.