General manager Craig MacTavish confirmed the injury timeline Tuesday morning through a post on the team's Twitter feed.
Hall, the first overall pick in the 2010 NHL Entry Draft, has three goals and five assists in nine games this season. He was hurt on an innocent-looking play in Edmonton's 3-1 win at Ottawa.
Hall was just inside the Senators' blue-line when he turned and hobbled to the bench. He left following the game with his knee in a brace but without the use of crutches.
"It's never good to lose one of your top players, a guy that eats up a ton of minutes, who's a danger every time that he goes on the ice," said head coach Dallas Eakins. "So are we going to miss him? Absolutely. Of course we are. He's a big part of this hockey club and when we do have success, he's right in the middle of it. He's usually one of the catalysts.
"But he's not here. So we'll look for him when he's healed and ready. It's time for other people to grasp opportunity."