CANTON, Ohio -- Dallas Cowboys left guard Nate Livings underwent a second surgery on his right knee in nearly six months, coach Jason Garrett confirmed Friday.

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.