Harding reportedly suffered the injury when he kicked a wall following an altercation with a team mate.
The 30-year-old is now on the shelf for at least two months, and will not receive pay until he is healthy enough to play.
The injury is the latest blow to Harding's NHL career.
Harding, who is in the final year of his contract, was diagnosed with multiple sclerosis in 2012. Harding has since played just 34 games over the past two season, and has been sidelined long-term due to side effects of the disease.
With just Niklas Backstrom left in the crease at Wild training camp, the club acted quickly to sign Darcy Kuemper to a two-year contract worth $2.5 million.
Kuemper appeared in 26 games last year in his rookie season, going 12-8-4 while posting a 2.43 goals against average and a .915 save percentage.
Kuemper will also join Ilya Bryzgalov at camp, who was invited Wednesday on a tryout contract.
Bryzgalov shined in 11 season games with the Wild last season, going 7-1-3, pushing Minnesota into the playoffs.
The 34-year-old helped upset the Colorado Avalanche in the first-round before being eliminated by the Chicago Blackhawks in the Western Conference semifinal.
The moves now give the Wild options in net.
If Bryzgalov prove he is a capable backup to Backstrom, Kuemper would be assigned to Iowa of the American Hockey League without having to go through the waivers process.