The issue was raised after a reporter from CBSSports.com noticed incision marks on Wells' knee.
Wells sat out the first two games of the season with what the team repeatedly had said was a bruised knee. Although he is listed as questionable for the home opener Sunday against Oakland, coach Ken Whisenhunt said there is "a very good chance" the second-year running back from Ohio State will play.
Whisenhunt did not mention the nature of Wells' injury in the coach's regular post-practice availability Friday.
But afterward, Whisenhunt confirmed the surgery to CBSSports.com and The Arizona Republic.
"It wasn't like a normal procedure where you're down X amount of weeks," Whisenhunt said. "It was a day-to-day thing. It was definitely something that we wanted to check out, but it wasn't ever anything that we thought was serious or that we thought would keep him from playing on a week-to-week basis."
Wells initially declined to comment on the incision marks, but spoke about the surgery after he found out it had been confirmed by the coach.
"I really wasn't worried about what people knew and didn't know," Wells said. "I had my knee scoped. I had a procedure done. I had to take some time off and I'm back from it."
NFL teams are known to fudge the facts on injuries, and reporters had long been skeptical about the bruised knee report.
Copyright 2010 by The Associated Press