The experienced Welsh centre toured New Zealand in 2005, making three appearances, and was originally selected for the 2009 tour of South Africa before a shoulder injury ruled him out of contention.
During his career Shanklin has scored 20 International tries in 70 appearances and was an integral part of Wales teams that won the Grand Slam in 2005 and 2008. He also featured for Wales throughout the autumn internationals but suffered a knee injury while on Magners League duty with Cardiff Blues in January.
He underwent surgery in a bid to get over the problem ollowing medical advice has made the decision to retire from the game.
"My knee isn't too bad, it's ok to walk and cycle and to do everyday things, but with regards to playing rugby: accelerating, changing direction, weight lifting, it's not too good," said Shanklin.
"I had an operation in January to see if we could fix the problem and it hasn't worked."
"It's bone on bone on my knee which has restricted me from doing a lot of things and I'm going to have to retire from the game."
"The advice from Rhys Williams the surgeon was to retire. Rhys knows the inside of my knee pretty well having done three or four operations on it."
"It was down to me to decide if I can continue or not, but I can't go on, as it's too sore and it's a pretty black and white situation. I can't fully function with it and I need to start taking account of my body and start listening to it."
"I'd like to thank not only Rhys for all his work, but all the Blues medical team who have been excellent in all they have done to keep me on the field for this long."
"I've had a history with a bad knee, but since 2005 it hasn't really troubled me. I've managed to carry on and continue until I injured it again January. I was aware at the time that it could end my career."
"A lot of the decision on whether I would retire was down to how my knee would recover and how I felt."
"I've now had time to take it on board, so it isn't a shock, and I've come to terms that I'll never play again."
"This summer I will be definitely spending more time at home with the family and enjoying my weekends."
"I'll still be watching the Blues and Wales but I'll be able to relax and maybe have a beer or two and watch some games with my mates."
"After that I'll be looking to get a job in the real world, which is a little bit daunting, but happens to all rugby players after they finish."
"Rugby doesn't pay like football so you need a job after, so I've been looking into that and will be starting to do some work for M.I.B. Construction."
Shanklin had a glittering career playing 114 times for the Blues scoring 28 tries and winning 70 Wales caps scoring 20 tries.
"I've been fortunate to have played with some great players and in successful teams, so any trophy that you win stands out in the memory," added Shanklin.
"The Grand Slams and EDF Energy Final were great days but I was gutted I couldn't play in the Amlin Final but maybe I played a part in the early stages."
"For me one of the games that really sticks in the memory is the Heineken Cup semi final against Leicester in the Millennium Stadium, just in the way the game had to come to an end."
"I still look back and think that was a crazy ending."
"Winning my 50th cap against Italy in the 2008 Grand Slam year is also one of my favourite moments."
"It was a great achievement for me and I remember the day very well. I scored a try as well so it makes it even more memorable. It was a great occasion."
Shanklin joined Cardiff Blues in the summer of 2003 having started his career with Saracens. Speaking of his time with the region, Shanklin concluded,
"Bob Norster, David Young and Peter Thomas have been massive influences in my career and I have to say that I've 100% enjoyed my time here otherwise I wouldn't have stayed so long."
"I've been very lucky to have the support of my wife and family who have been great, but also had support from some of my good mates."
"I've made some great friends through rugby that I will have for life and I've been lucky that it's given me so much."
"The whole team has made the Blues a great place and a great environment and I'll definitely be down watching the games."
"I still want to be part of the Cardiff Blues community."