Aluko missed the second half of the 2012-13 season with a similar problem and Bruce said his heel had flared up again in the warm-up ahead of Saturday's 1-0 victory over nine-man Sunderland.
The Nigeria striker had persuaded Hull's medical staff he would be able to play in that game after overcoming a calf injury but he ended up being a late withdrawal from the squad.
A scan has now confirmed the extent of the damage, which is likely to keep the 24-year-old out until January at the earliest.
The news is a big blow for Bruce, who has had to deal with a number of injuries this season including to key players Robbie Brady, James Chester and Allan McGregor.
So far this season, only Brady (three) has scored more than one goal for the Tigers in the Premier League but they have proved sound defensively, especially at home where only one goal has been scored by an opponent in five matches.
Aluko's absence is likely to mean an extended run in the side for Yannick Sagbo, who has started their last two games since coming off the bench to score against Everton.