The Ducks announced the prognosis for their high-scoring defenceman's injury Wednesday.
Fowler has missed Anaheim's last two games with the injury, which could keep him out for the remainder of the regular season. He was hurt in the second period of a game in Colorado on March 14.
The Ducks' season ends April 13.
Fowler is enjoying a breakout season with six goals and 30 assists in 67 games. He is Anaheim's fourth-leading scorer and its ice-time leader with nearly 24 minutes per game.
Fowler also played for the U.S. Olympic team in Sochi.
Anaheim also will face San Jose on Thursday without centre Nick Bonino, who injured his foot Tuesday night.