The 25-year-old left winger sprained the medial collateral ligament in his left knee with about five minutes left in the second period. He limped to the bench but came back on the ice with about one minute remaining in the frame. That was his final shift of the game.
An MRI taken Tuesday revealed the sprain that will sideline him for three to four weeks.
It was the latest blow to the Rangers, who have been hit by several recent injuries as they try to climb back into playoff position.
New York is already without Brendan Shanahan, who hasn't played since Feb. 17 when he collided with Philadelphia forward Mike Knuble and sustained a concussion. Shanahan is recovering but is still having bouts of vertigo as a result of the injury. He is still at least a week or two away from returning.
Defenseman Fedor Tyutin is also out for the next three or four weeks because of the same injury as Hossa. He was hurt Thursday against Pittsburgh.
Left winger Martin Straka returned against the Islanders after missing three games with a shoulder injury.
The Rangers recalled forward Brandon Dubinsky and defenseman David Liffiton from AHL Hartford on Tuesday.
Hossa was playing his best hockey of his five-season NHL career. He has 10 goals and eight assists in 64 games, but 13 of his points -- including eight goals -- have been scored in his last 15 contests. Since the All-Star break, Hossa has a team-high eight goals.