Allen had 55 total tackles and two interceptions for the Steelers last season.
Allen had sat out of practice for the past few days with was was diagnosed as knee discomfort. The team drafted Allen, who played his college football at The Citadel, in the 4th round of the 2011 draft.
"Earlier today, Cortez had minor surgery on his right knee. We wanted him to get the surgery done now so he can begin rehabilitating immediately. This surgery was a minor procedure and will have no long-term effects on his return to the field. We look forward to his rehabilitation process and having him back on the field in a couple of weeks," Tomlin said.