Irving, TX (Sports Network) - The Dallas Cowboys have placed defensive end Anthony Spencer on injured reserve because of a knee issue that will require surgery.
Spencer will undergo a microfracture procedure on the same knee that needed surgery in July. He didn't play during the preseason while recovering from the operation and sat out the club's season-opener against the New York Giants before returning for the Week 2 contest against Kansas City.
The 29-year-old Purdue product notched a pair of tackles in the loss to the Chiefs, then was inactive for this past Sunday's game against St. Louis.
A 2007 first-round pick, Spencer was coming off an outstanding 2012 season in which he set career highs of 11 sacks and 95 tackles. He is set to become an unrestricted free agent in the offseason after being designated as Dallas' franchise player for 2013.
The Cowboys filled the roster spot by signing cornerback Chris Greenwood off the Detroit Lions' practice squad. Greenwood, a fifth-round Lions draft pick in 2012, missed his entire rookie season because of a torn abdominal muscle and was signed to Detroit's practice squad earlier this month after being among the team's final cuts.