Knox is a 2003 Macalester graduate who earned two time all-American honors for the Scots soccer team. Knox then started his professional career with the Thunder in 2005. For the Thunder, Knox netted five goals and four assists in 20 appearances.
Knox was an important striker for the Thunder in 2006, scoring a key goal in a July game to beat Montreal who was currently in first place in the First Division standings.
Knox has played in eight games for the Silverbacks this season, netting one goal.
"Aaron has been a great ambassador for the Thunder over the years," said Thunder president Manny Lagos. "We appreciate what he has done for this club and wish him the best at Atlanta and expect him to succeed there."
"We are looking forward to having Nate Knox playing for the Thunder again," said Thunder head coach Donny Gramenz. "Nate is a player that is going to add instant professionalism and playing quality to the Thunder organization. He gives us size, a great work ethic, and intelligent and selfless runs that will create goal scoring opportunities for himself and his teammates."