Brown suffered medial and possible cruciate ligament damage which will keep him out until the end of the season.
Brown may yet need to undergo major surgery on his knee which would mean an even longer spell on the sidelines.
“At this stage we know for definite we’ve lost Kev for the rest of the season,” said Huddersfield coach Nathan Brown.
“The extent of the medial ligament damage he’s suffered means there’s no way he’ll make it before the play-offs are over.
“We’re still waiting to see if he’s suffered cruciate damage as well, but to be honest, we didn’t feel the need to hurry the scans.
“We already know he won’t make it before the end of the season and we were travelling back on Sunday and had the civic reception yesterday.
“If there was a chance he could play again this year, we’d have had the scans done straight away, but in the circumstances, there was no need to rush.”
The Giants travel to Celtic Crusaders on Saturday and host Wigan Warriors the following week in the final game of the regular season.