Moreno suffered the injury during the first quarter of Sunday's 17-10 victory over Kansas City.
"He'll be out for the season. We'll place him on IR. It's an ACL injury that will require surgery," Fox said.
The Georgia product carried the ball 37 times for 179 yards in seven games this season for Denver. Moreno also caught 11 passes for 101 yards and a score.
Fellow running back Willis McGahee sustained a hamstring injury during Sunday's game, but his situation doesn't seem as severe.
"He was cleared to come back in the game, we weren't going to put him in there unless it was an emergency," Fox said of McGahee.
The 4-5 Broncos play the Jets on Thursday night.