Former Olympic champion hurdler Liu Xiang has confirmed his retirement more than two years after his last race, citing age and injuries. The 31-year-old Liu says on his microblog yesterday the decision is sad and painful, but felt he had no other choice after years of nagging injuries. The Shanghai native hasn't competed since withdrawing at the London Olympics in 2012 after rupturing his Achilles tendon. He pulled out of the 2008 Beijing Games with a similar injury, and years of treatment have apparently failed to fix the problem. Liu became one of China's best-known athletes by winning the 110-meter hurdles at the 2004 Athens Olympics in a then-world record time. He went on to become one of the country's highest-earning sports stars.