Smith suffered the injury while on the punt-coverage unit early in the fourth quarter. He had to be helped off the field and was on crutches following the game.
The loss of Smith takes away one of the Falcons' most dangerous offensive weapons. He currently is tied with Roddy White for the team lead with five touchdowns. Smith also was one of the Falcons' best special-teams players.
Smith is in the final year of his contract, and Falcons owner Arthur Blank expressed a desire to have Smith back for years to come.
Antone Smith was the eighth Falcons player to be placed on season-ending injured reserve since June. The team first lost Sean Weatherspoon to an Achilles tear. Offensive linemen Sam Baker (knee) and Mike Johnson (foot) were lost during the preseason, then offensive linemen Joe Hawley (ACL), Peter Konz (ACL) and Lamar Holmes (foot) went down during the season. Rookie linebacker Marquis Spruill (ACL) also is among the group.
Starting strong safety William Moore was placed on IR with a designation to return on Sept. 30 after suffering a shoulder injury in Week 4. Moore is eligible to play again in Week 13 against Arizona following the eight-week window for sitting out from when he was placed on IR.