Lucas Braathen scored but crashed right at the finish line after he hit the last gate and lost his balance.
He was cared for on the slopes before being taken to hospital.
The TV pictures showed how he got to his left knee.
Now the Norwegian Ski Association announces that Braathen has sustained a ligament injury on the inside of the knee.
- It requires surgery.
We will now get him home for a final assessment, but the season is over.
The rehabilitation period after such an injury is normally between six and nine months, says Norwegian national team leader Marc Strauss in a press release.
Lucas Braathen took his first World Cup victory in October.
ARCHIVE: Braathen took his first VC victory
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Lucas Braathen celebrated after the victory in Sölden.
Photo: Bildbyrån