Christiansen has competed in four Paralympics starting in 2000 in Sydney, Australia where he finished sixth in the shot putt for F44 athletes. He later improved on this, winning gold in 2004 in the F44/46 class and in 2008 in the F44 class. He also won two silver medals in the discus, in the F44/46 class in 2004 and the F44 class in 2008. He won the F42/44 shot put gold medal at the 2012 Summer Paralympics in London.