The Browns issued a statement Thursday saying the running back, drafted No. 3 overall, had what the team termed "routine arthroscopic" surgery by Dr. James Andrews in Pensacola, Fla.
Sources told ESPN's Chris Mortensen on Wednesday the surgery would remove a "hang nail particle" of loose cartilage that was irritating Richardson's knee.
Richardson is expected to return before the regular-season opener, the sources told Mortensen. Another team source described the recovery as a "two-week deal."
Andrews did a similar procedure on Richardson on Feb. 3 to repair a torn meniscus the running back suffered in the same knee while playing for Alabama during its BCS national championship victory over LSU.
Coach Pat Shurmur, with the team in Detroit where the Browns open their preseason on Friday night, issued a statement saying he hoped Richardson would be able to return by the season opener on Sept. 9.
"We anticipate that Trent will make a speedy recovery, and we are hopeful that he will be ready for our Week One game against Philadelphia," Shurmur said.
Richardson sat out practice for the first time Tuesday with soreness in the knee.
Montario Hardesty will start in place of Richardson against the Lions. It will be an opportunity for Hardesty to see how far he has come back from knee surgery two years ago.
"It's a chance for the whole team to go out and show what they can do," said Hardesty, a second-round choice in 2010 who was injured in preseason that year and missed his entire rookie year.
"I'm excited, but I would be anyway. It will just be good to go out and face another team and show what we, collectively, have done to improve."
Shurmur said Chris Ogbonnaya, a midseason pickup from Houston last year, and former Green Bay running back Brandon Jackson also will see time. Jackson hurt a toe during the Browns' preseason game against Detroit last August and though he did not need surgery, missed the entire season.
Information from ESPN's Chris Mortensen and The Associated Press was used in this report.