Johnny Knox has announced that the back injury he sustained over a year ago has ended his playing career.

The wide receiver was released from his contract with the Chicago Bears earlier this week, having not been able to play since December 2011.

The 26-year-old told the Chicago Sun-Times: "As an athlete, you don't want to give up, you want to keep fighting. That's how I've always been. But it's been on my heart for a while now.

"I know how my body feels, and I know I'm not going to be the same and perform at the ability that I used to. So I'm moving on and going forward.

"I was centimetres away from being paralysed, so just sitting here and talking, I'm appreciative of that, just the hard work that I had to put in, just to be able to stay in and do everything in my daily life that I used to do."

Knox sustained the injury during a game against the Green Bay Packers, when a collision with a defensive end left him needing 10 minutes of treatment on the field before being taken to hospital for surgery.

Knox was the Bears' leading receiver during the 2010 season.