Umenyiora was hurt in the second quarter of Saturday's preseason game against the New York Jets, and Dr. Russell Warren told the team on Sunday that an MRI found a tear in his lateral meniscus.
"It was obviously the news that I did not want to hear," coach Tom Coughlin said. "But after listening to the explanation and Dr. Warren's thoughts on it, I am convinced that this is the right procedure and the right way to go."
The normal recovery lasts four months, Coughlin said, adding that a non-surgical option was not discussed.
Coughlin said the team is considering all its options when asked whether the Super Bowl champions were interested in luring the 36-year-old out of retirement.
Coughlin recently talked with Strahan about his new career working on Sundays for FOX Sports.
"The only thing I talked with Michael about was his new challenge, moving forward in his new assignment and he was very excited about that," Coughlin said.
Strahan, meanwhile, is currently on vacation and hasn't heard from the Giants. On the possibility he would return to the Giants, Strahan told NFL Network's Adam Schefter: "I haven't heard from anybody else so to say if I would or wouldn't is premature. So I'm enjoying my retired life right now."
This is not the first time Umenyiora has required surgery to repair cartilage damage in his left knee. He underwent arthroscopic surgery for the same problem at Troy State.
With Umenyiora out, the Giants have to consider moving strongside linebacker Mathias Kiwanuka back to defensive end. He was switched to linebacker last year so the team could put its best 11 players on the field.
"I haven't had a chance to talk to him so I am not going to comment on that," Coughlin said.
Copyright 2008 by The Associated Press