Head coach Mike Shanahan reported after practice Monday that left guard Kory Lichtensteiger injured the cartilage his knee during the first week of practice, requiring arthroscopic surgery.
"It was a little sore, and so he had an MRI just to make sure, and that's when we found those particles," Shanahan reported after practice. "Just talking to [the doctors], he thought it'd be smart to go in there and clean those particles out of the cartilage, rather than him waiting a week or two to see if it improved and him having that soreness."
Lichtensteiger started the first five games of the 2011 season before tearing his ACL and MCL against the Philadelphia Eagles in Week 5.
He injured the same knee last week, but without the long-term concern.
"The good part about it is the ACL's fine, the MCL's fine," Shanahan said. "Any time you get in to scope, the guy should be back fairly quickly, so hopefully that's the case."
Shanahan said he was optimistic that Lichtensteiger could return in time for the third preseason game against the Indianapolis Colts, but that was unlikely.
Instead, Shanahan said he would rather have Lichtensteiger rehab properly and return for the first regular season game against the New Orleans Saints.
"I think you have to be very patient with Kory, just because you don't want to lose a player for the season," Shanahan reasoned. "The doctors thought it was in his best interest to get it cleaned out, and hopefully he's ready to go full-speed."
Shanahan reported that second year offensive guard Maurice Hurt and rookie lineman Josh LeRibeus would continue to split time at the position until Lichtensteiger returned.
Hurt filled in for Lichtensteiger as a rookie in 2011, starting the last eight games of the season at left guard.