The former Hammarby player, who was selected for the latest men's national team squad, was carried off on a stretcher in Friday's match with his club team Coventry.
"As we feared, he has sustained a cruciate ligament injury that will end his season. He will undergo an operation and we are very sorry for him", says coach Frank Lampard in a statement on the club's website.
The 22-year-old joined the English Championship team last year and has played 30 matches this season.
"He has had a fantastic season and the progress he has made since we (the new coaching team) arrived here makes this a bit more bitter, since he has played so well", continues Lampard.
Coventry is currently fifth in the Championship and, with seven rounds remaining, has a good chance of securing one of the playoff spots for the Premier League.
What do you think?