Ibrahimovic suffered the injury during Manchester United's 2-1 victory over Anderlecht in the Europa League.
The Swede looked in severe discomfort and speaking to journalists at his press conference on Friday United manager Jose Mourinho said that the forward's situation didn't look good.
Now a report from Sky Sports says that Ibrahimovic will miss the end of the season which will rule him out of the Europa League semi-finals.
A further report from the Telegraph said that there are fears that Ibrahimovic has ruptured both the anterior and posterior cruciate ligament in his right knee and could be out until Christmas whilst ESPN say he won't play again until 2018.
Of course as things stand it would mean that Ibrahimovic would have played his final game for United, with his contract set to expire at the end of the season.
Read the full article on eurosport.co.uk: Ibrahimovic to miss rest of season with serious knee injury - reports