Ahead of the cinch Premiership game against Livingston at Ibrox on Wednesday night, where midfielders Ryan Jack and Scott Arfield are back in contention, Van Bronckhorst said: “He had a knee operation. He needed reconstruction. We won’t see him this season.
“It is a serious injury so it is bad news. It is a big blow. An important player is not available for the coming months so we are looking to add a player to the squad but he needs to be a player we think is right.
“You don’t want players in to make up the numbers. You want to have the balance in the team also good but we are definitely looking to add a player in the coming days.
“I spoke to Ianis this morning, he is in a good place, of course not happy that he has the injury and needed the operation but he’s positive and focused on his recovery.
“We won’t have him for months so that is the bad news for us, the good news is we have Ryan Jack and Scott Arfield back in the squad tomorrow.”
As well as having Jack and Arfield available for selection, attacker Joe Aribo is on his way back from the Africa Cup of Nations after Nigeria were beaten by Tunisia in the last-16.
Van Bronckhorst said: “It is good to have Joe back. It was not a good result for him at the weekend. It is sad for Joe that he couldn’t play on in the tournament.
“He is travelling back today and he will be back in Glasgow tonight so we have to assess him, if it is smart for him to be in the squad tomorrow. He will for sure be available for the weekend and after that.”
Van Bronckhorst is expecting a tough test against Livi, whom Rangers beat 3-1 in West Lothian in November.
He said: “We have to make sure we keep our standards and our way of playing and make sure we go for 90 minutes to win the three points.
“They have shown this season already that they can be very hard to beat. In the away game, we had a tough game and scored the third goal later than we wanted.
“They are quite a good team with a good spirit, they keep it compact so we have to make sure we are on top of the game to get the three points.”