Ospina only joined the club this summer after starring for Colombia at the World Cup, but with Wojciech Sczcesny suspended after a red card against Galatasaray, Arsenal will have to turn to young Emiliano Martinez for the Champions League game against Anderlecht on Wednesday.
“It is exactly the same (injury). He had his first injury in Nice, it was a knee problem and I think he was a bit rushed back,” Wenger told a news conference.
“He didn’t use his legs so his muscle became weaker, then he got injured during the World Cup. And after that he came to us injured, from the World Cup. It took him two months to play a game.
“I had to bring him on against Galatasaray without a warm-up, without being prepared and he had a recurrence of that injury. That means he is out for two to three months.
“Now we have to be really careful because he has a recurrence of a thigh injury that’s very difficult. It’s a long-term injury.”
Wenger gave his backing to novice keeper Martinez, who will step in for the match in Belgium.
“I am extremely confident with him,” he said of 22-year-old Argentine. “He has experience from [a loan spell at] Sheffield Wednesday last year and when he played for us he did very well. I have no special worry about that.
“He has good experience; he has grown in stature as well. I believe we have to make sure it is as comfortable a night as possible that is by defending well as a team.”