As an amateur Knoetze fought future professional world champion and fellow South African Gerrie Coetzee six times, each winning three bouts.
In his seventh fight he was disqualified against Reinaldo Raul Gorosito, and in his eighth bout he lost a ten rounds points decision to Coetzee.
In the other elimination bout, Coetzee defeated Leon Spinks and then went on to lose to Tate for the WBA title.
He fought seven more bouts, winning four and losing three, before retiring in 1981 after a second-round knockout loss to Robbie Williams.
Between 1979 and 1991 Knoetze acted in four movies, his best known role being primary antagonist Rosco Dunn, a former corrupt professional boxer-turned-military sergeant, in the 1982 film Bomber.