Knowles played college soccer for the University of Akron, captaining the team his senior year. Knowles anchored an Akron defence that allowed only three goals in league play and recorded 13 shutouts in 2004. Knowles, a two-time All-Mid-American Conference first-team selection led Akron to two MAC titles in 2002 and 2004 and helped Akron make four consecutive NCAA tournament appearances. He was selected to the All-MAC second team his freshman and sophomore seasons and voted Akron's Newcomer of the Year in 2001. In addition, Knowles was a College Soccer News All-Freshman Team honourable mention. A testament to his durability, Knowles played in 49 straight games during his career at Akron. Knowles also played in the USL Premier Development League for Chicago Fire Premier making 14 appearances and scoring two goals in league play. In addition, Knowles scored 3 goals during the Fire's 2004 Lamar Hunt U.S. Open Cup campaign.
Professional
Knowles was drafted by Real Salt Lake of Major League Soccer in the fourth round of the 2005 MLS Supplemental Draft, becoming the first Akron Zip to be drafted by a Major League Soccer team. He made his professional debut on 22 June 2007 against the Los Angeles Galaxy and totalled 346 minutes in four matches his rookie season in MLS, but did not make an appearance at all in 2006 and was released at the end of the year. Knowles signed with the Portland Timbers of the USL First Division in 2007, and played in all 28 regular-season matches in his debut season for the team, scoring two goals and being named as one of three finalists for the USL First Division Defender of the Year award. He started 29 of 30 matches for the Timbers in 2008 was named to the USL First Division All-League second team. In August2009 Knowles sustained a serious leg injury in Montreal that sidelined him for the rest of the season and part of 2010. Knowles was picked up on 26 July 2011, by the Montreal Impact. Knowles made 8 appearances for the Impact before retiring at the end of 2011. He was released by Montreal on 12 October 2011.
International
Knowles was selected in the New Zealand under 17 squad for the FIFA World Championships but did not participate in the tournament has he suffered a broken leg three weeks prior to the opening match.
Coaching career
On 26 January 2012, the Portland Timbers of Major League Soccer announced the addition of Knowles to the coaching staff as an assistant under Head CoachJohn Spencer.
