3:24PM BST 11 Jul 2011
The 31-year-old former England international started out at Leeds before having spells with Newcastle, Real Madrid and Middlesbrough in a career blighted by injury.
Speaking from the club's pre-season training camp in Austria, manager Tony Pulis said: "The lad is a top-class player and it's been well documented that he has had his injury troubles, but we believe that if his fitness is managed properly, he will play games for us.
"We know that other Premier League clubs were keen on signing Jonathan, so we are delighted he has chosen us. It's a chance we are taking, but one we were keen to take because of the stature and quality of the player."
He added: "We've effectively taken him on a pay-as-you-play deal which just shows how desperate the lad is to get his career back on the right track."
Stoke chief executive Tony Scholes added: "There is no doubt that we have acquired a player with outstanding quality and experience but he is one who has clearly struggled with injuries over the past two years.