Ozil, 26, first felt pain in the knee during Arsenal's 2-0 Premier League defeat at Chelsea on October 5 but Wenger told reporters on Thursday that the German did not reveal the gravity of the issue at the time.
"I didn't even know about it. At halftime, just before we went out, the physio told me he had a little pain in his knee but its not bad and he wanted to go on," Wenger said.
"I told him 'if you don't feel well tell me and I will take you off straight away' but he never did in the whole game and I left him on because we needed to find a goal,” he added.
He then joined up with the Germany squad during the international break and the German FA have confirmed he had a partial tear of a ligament in his left knee.
"They described it as serious," Wenger added.
As well as missing Saturday's match against Hull City, he will also be unavailable for upcoming games against Anderlecht and Borussia Dortmund in the Champions League, and Manchester United in the Premier League.

Defender Laurent Koscielny will also miss Saturday's match with an Achilles injury that kept him out of the France squad over the international break.
However, some good news for Arsenal is that Theo Walcott, Mikel Arteta and Serge Gnabry have all resumed training after recovering from injury, and Aaron Ramsey will start training again next week.
England winger Walcott is set to make his first appearance for nine months in a Premier League under-21 match against Blackburn Rovers on Friday.
Walcott, 25, has not played for Arsenal since rupturing his anterior cruciate ligament during the 2-0 win against Tottenham Hotspur in an FA Cup third round match in January.

Latest News from Sports News Desk