The star QB was making his first start of 2014 following off-season surgery to the same shoulder.
"Travis has suffered a shoulder dislocation very similar to the one he had last season," Dr. Bob McCormack said in a statement. "Due to the nature of the injury, the surgery which was performed on Travis' shoulder last winter has essentially been undone."
The Lions said Lulay will be placed on the six-game injured list and that his playing status will be reviewed by doctors and training staff as the season progresses.
Lulay separated the same shoulder — on his throwing arm — last September against the Montreal Alouettes but returned to action in the final week of the regular season before opting for off-season surgery.
It was hoped that he would be ready for training camp in June, but the recovery took much longer than expected. Lulay dressed for three games as a backup before starting B.C.'s 7-5 victory over Ottawa.
The injury occurred late in the game when Lulay was attempting a pass. The ball slipped out of his hand and as he scrambled to recover the fumble, he got caught up in a pile of players.
Lulay is expected to meet the media on Tuesday afternoon at the club's suburban practice facility.
Kevin Glenn started the first nine games of the season at quarterback for the Lions, leading them a 5-4 record.
B.C. hosts the Winnipeg Blue Bombers on Saturday.