The striker has managed just one bench involvement, against Wolves, this season and now faces having to sit out the season until January.
Asked about the news, his agent Tore Pedersen told VG: "Of course Stefan would like to be in the squad, but now he has two months to fix a couple of minor injuries that have bothered him this fall."
Johansen has a contract with Fulham until 2022.
He featured for Norway earlier this month in international action.
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