Powell has made 40 European appearances in 11 years in spells at Ebbw Vale, Cardiff Blues, Worcester and then Northampton and is disappointed to have his playing days cut short.
"Obviously I'm gutted and devastated that my career has finished this way," he said.
"No player wants to retire, whether it's part of a natural process or because of injury - you want to think you can go on forever. It's been a massive shock and it probably won't sink in until I'm watching the players running out and I'm not a part of it.
"It's been great at the club and I've enjoyed myself. I played a lot more rugby than I was expecting to play, and enjoyed being part of a squad that was part of the Heineken Cup final. All in all it's been a great part of my career.
"Playing for my country was my major career highlight - it's every young kid's dream and I was lucky enough to play for Wales, which was a massive achievement. Cardiff was my first club, I was there for a long time, and Northampton was a fantastic opportunity for me towards the end of my career.
"I'd like to thank everyone who has helped me in my career - there are too many people to pinpoint anyone in particular - but I'd like to thank Jim and the coaches at Northampton for giving me the opportunity."