The Ghanaian youngster has been with Blues since 2012 after being spotted playing for Southern League side Woodford FC as a schoolboy.
Arthur is a powerful striker of the ball and can play any across the middle of the park or in a more advanced role.
He made his Blues debut as a late substitute against Wolves on April 1, 2013.
His progress during his debut campaign was recognised with him receiving the Academy Player of the Year Award for 2012/13.
Arthur spent a month out on loan at League Two side Cheltenham Town at the start of the 2014/15 season, where he scored four goals in eight appearances for the Robins, before being recalled by Blues.
Arthur signed a new two-year deal with Blues in June 2015.
In August 2016 Arthur joined League Two side Cheltenham Town on loan for a second time on loan and made seven appearances before returning to Blues in January 2017.