Tuhia he haere tonu mo tenei whitianga - He tangata no Needham, Massachusetts, i tae atu a Arnold ki te takaro i te hockey kura tuarua i Noble me Greenough School me te kaupapa Boston Junior Bruins i mua i tana urunga ki te USA Hockey National Team Development Program mo te waa 2009-10. I te taumata U-17, ko Arnold te rangatira o te roopu o te roopu whiriwhiri i uru ki te whakataetae a nga iwi e rima i Slovakia; i whakaingoatia ia hei kaitakaro tino nui o te whakataetae. I te 2010 IIHF World U18 Championships, i tuhia e Arnold nga tohu e toru i roto i nga keemu e ono i te National Team Development Program, e tohu ana mo te United States, i toa i te mētara koura. I te 2010 National Hockey League (NHL) Whakauru Whakauru
I whiriwhiria a Arnold i te rauna tuawha, 108th katoa, na Calgary Flames.