Karanka, younger brother of former Athletic Bilbao, Real Madrid, Colorado Rapids and Spain central defender Aitor Karanka, came up through the ranks of the Basque giants and first appeared with the main side on May 14, 2000, playing 15 minutes of a 0-0 draw at RCD Espanyol.
After a loan stint to CF Extremadura in 2000-01, where he scored 13 Segunda División goals, Karanka returned to Athletic, with virtually no impact (six matches, although he scored once, in a 3-2 thriller success at Celta de Vigo, as Bilbao trailed 0-2 with 8 minutes remaining).
Karanka then returned to the second level, helping Real Murcia achieve promotion in 2002-03, netting 13 goals and adding 7 in next season's top flight, as Murcia returned to where they came from.
After two seasons, he was transferred to fellow league side Sporting de Gijón where his form deteriorated, scoring only twice in 33 games over two seasons.
In January 2008, Karanka joined Real Unión, in Irún, Guipúzcoa, moving in August to another Segunda División B outfit, UE Sant Andreu.