Redman announced his retirement on his Twittter account.
"Why I'm not in the NFL?" Redman wrote. "To those who are wondering why I am not playing anymore. Last season, I tried my best to play through a neck injury, but I just wasn't myself on the field."
After undergoing two magnetic resonance imaging exams and a CAT scan, the doctor informed Redman that his football career was over.
"He told me I suffered a career-ending injury to my spinal cord," Redman wrote. "Various teams have called, but as you can see I was unable to go. I would like to thank all my fans for their tremendous support throughout my career."
After going undrafted in 2009 out of Bowie State, Redman forged a solid career with the Steelers. In five seasons, Redman rushed for 1,148 yards and five touchdowns on 282 carries.
Redman was released by the Steelers last year after he suffered a concussion.