Ronnie Barnes, the Giants' vice president of medical services, called the procedure "a simple debridement."
Umenyiora is expected to be out 3-to-4 weeks.
The 29-year-old had been at odds with the organization over his contract and recently returned to camp following a brief holdout. He experienced swelling in his knee after three practice sessions, according to general manager Jerry Reese.
Umenyiora is entering his ninth year in the NFL, though he missed the entire 2008 season because of a torn knee ligament. Umenyiora had 11 1/2 sacks with 10 forced fumbles during the 2010 campaign.