The Peterborough United midfielder, capped 17 times by Wales, dislocated a kneecap playing for West Ham in 2009 and will now focus on a coaching and media career.
"The nights I wake up in pain, or the mornings where I struggle to walk, will be a constant reminder I was lucky enough to play the game I love," he told The Sun.
"I still wake up some mornings feeling good and think 'one more try'.
"But that would be unfair on myself, my fellow pros and my family. I want to bow out with some pride intact."