The expected recovery time is 5-6 months.
Vaakanainen, who had not played since Jan. 28 and has been on injured reserve since Feb. 6, has two assists in 23 games this season.
The 24-year-old previously missed 22 games at the start of this season after crashing into the end boards during a preseason game against the San Jose Sharks on Sept. 30. He was taken off the ice on a stretcher and briefly hospitalized.
Ducks center Adam Henrique could also miss the rest of the season because of a sprained MCL. He was originally expected to be out 5-6 weeks after he sustained the injury in a 6-1 loss at the Tampa Bay Lightning on Feb. 21, but he has not progressed and is expected to be out another 5-6 weeks.
Henrique has 33 points (19 goals, 14 assists) in 57 games this season.
Anaheim (21-34-8) is seventh in the Pacific Division..
