Knighton played four years of college soccer at UNC-Wilmington as well as for Indiana Invaders in the USL Premier Development League.

Undrafted by Major League Soccer, he attended a New England Revolution tryout in early 2007 and was good enough to be invited on trial for the preseason.

After spending his first year and a half with the Revs behind Matt Reis and Doug Warren, he was loaned to the Portland Timbers on July 2, 2008, for the remainder of the 2008 Major League Soccer season.

He made his league debut for Philadelphia on August 8, 2010, against FC Dallas away, but was sent off for denying of an obvious goalscoring opportunity in 22nd minute.

In his next start, he shut out the Chicago Fire at PPL Park on September 11, 2010, earning his first professional clean sheet, and also Philadelphia's first in franchise history.