Livings' first surgery was in February. He aggravated the knee during organized team activities in May and hoped rest would take care of the issue. He missed the early part of training camp because of a cut on his foot but returned to the field and took over his first-team snaps. He sat out of Thursday's practice because of knee soreness.
The typical recovery time from a scope is two to four weeks, which would put Livings' availability for the season opener against the New York Giants in doubt. Livings is the second starter to need knee surgery in camp, joining linebacker Anthony Spencer.
Injuries have ripped apart the offensive line since the start of training camp.
Last year's starting right guard, Mackenzy Bernadeau, was finally cleared to practice Friday after sitting out the first two weeks of camp because of a hamstring strain suffered in the team's conditioning run. Ronald Leary, who is competing with Livings for a starting spot, returned to practice this week after missing time with a back injury. Tackle Jermey Parnell has missed most of the practices with a hamstring strain. Center/guard Ryan Cook has been kept out recently because of an achy back. Guard Ray Dominguez has a shoulder injury. Guard Kevin Kowalski is out two to four weeks with a bruised knee. Conditioning has kept tackle Demetress Bell from practicing.
On Thursday, the Cowboys signed linemen James Nelson and Jeff Olson to help get through practices. Veteran Brian Waters, who did not play last season after a Pro Bowl season in New England, is also on the Cowboys' radar.
Livings started every game last year after joining the Cowboys as a free agent. His $1.7 million base salary is guaranteed this season.