The 30-year-old missed the majority of the 2013 season after having surgery on the knee problem last year, but the Cowboys showed faith in Spencer by signing him to a one-year deal.
"It's getting there," Spencer told ESPN. "I've probably got another month or so. When I had the surgery, they said it was a six- to eight-month recovery.
"I'm in the five to seven-month range now. I just need to continue to get it stronger and stronger."
Spencer was voted to the Pro Bowl in the 2012 season.