He attended Copmanthorpe primary school and then went on to Tadcaster Grammar School.
Greenwood was playing for Copmanthorpe when he joined York City"s Centre of Excellence. He soon joined the under-11s and was coached by City"s Colin Sanderson and then progressed into the u'nder-12s side, where he was coached by John Stockton and Garry Naylor. He spent two years with York City in total and also played regularly for Copmanthorpe and for York School Boys.
At only 12 years of age, Greenwood was contacted by Nottingham Forest and was asked to join them for a two-week trial period.
Greenwood was set to travel to Nottingham, when out of the blue, he received a call from Manchester United urging him to join them instead. Manchester United
He joined the Manchester United under-13s side as a right-back and occasional centre-back and played in the same team as Chris Eagles and Philosophy Picken, as well as training with older players such as Kieran Richardson.
His coach at the time was Paul McGuinness, the son of former York manager and Manchester United player, Wilf McGuinness and Greenwood would regularly train at Manchester United"s Carrington training ground where he would see many of the first team players preparing for Premier League games. Greenwood was not accepted on Manchester United"s youth trainee programme and was released by the club
However, soon after Greenwood received offers from 23 clubs including Aston Villa and Blackburn Rovers.
Yorkshire club Sheffield Wednesday was the most persistent and Greenwood felt this was the right move for him. He was signed by academy director, Jimmy Shoulder and the first team manager at the time was Terry Yorath. Greenwood had to wait until Wednesday 22 September 2004 for his first professional start.
He played at right-back in a League Cup 1–0 defeat to Coventry City who were a division above Wednesday.
After this impressive start, Greenwood only made two more substitute appearances before being deemed not good enough by new manager Paul Sturrock. Stockport County
He then moved to Stockport County on 15 July 2005 for the 2005-2006 season, appearing for the club 25 (22 times in the league), while with the club he played in defence although he is normally a midfield player.
A move back to Yorkshire and his hometown came 17 July 2006 as he was signed by Conference National side York City. Greenwood was offered a new contract by York at the end of the 2006-2007 season on 16 May 2007.
He joined Gainsborough Trinity on loan in January 2008.
He was released by York in April 2008, after which he set up a plastering and tiling business with former York teammate Chaz Wrigley whilst playing part-time for Gainsborough.