Knowles anchored an Akron defence that allowed only three goals in league play and recorded 13 shutouts in 2004.
In addition, Knowles scored 3 goals during the Fire's 2004 Lamar Hunt U.S. Open Cup campaign.
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.
[3] 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.
[5] On 5 January 2024, Knowles was announced as the interim head coach for Minnesota United following the departure of Sean McAuley.