He began his youth career in the local club Orkdal IL, before moving on to Rosenborg in 1978, where his father was the head coach.
[2] Moss stayed in Tippeligaen under Eggen's command, and after the 2001-season he became coach of another club from Østfold, the old giants, Fredrikstad FK.
When Olsen retired from the position at the end of the year, due to health issues, Eggen was once again promoted to his previous job.
After this very successful season, Eggen quit his job in Fredrikstad in December 2006, after several major disagreements with new club director Morgan Andersen.
[5] However, in an interview with Verdens Gang in October 2013, his father Nils Arne Eggen told that Knut Torbjørn chose to end his own life after years of struggling with anxiety disorder which got progressively worse, and that "In the end, his fear of living became greater than his fear of dying.