He earned multiple All-American accolades in shot put and discus while attending Western Maryland and Penn State.

While attending BYU, he was coached by Jay Silvester, an American discus legend and former world record holder.

[6] Hjeltnes coached at the NCAA Division I level for about 20 years, producing a number of All-Americans and conference champions.

Hjeltnes tested positive for anabolic steroids at Oslo's Bislett Stadium on 6 July 1977, and at the European Cup in Helsinki in August 1977, and was suspended "indefinitely."

Knut also cooperated with Jan Hedenstad to write a book, called Dopet ("Doped"), published in 1979 (ISBN 8205120021).