Knetig has worked with the National Philharmonic in Warsaw since 1981 and the Kraków Opera since 1982. He joined the Warsaw Chamber Opera as a soloist in 1986 and has travelled all over Europe with this group. He has sung at many festivals, including Wratislavia Cantans, Warsaw Autumn, Berliner Festwochen, Caryntiche Sommer, Salzburger Festspiele, The European Music Festival in Berlin and Tokyo, and the Monreale Oratory Music Festival in Palermo. He has been invited to sing in operas and oratory concerts in many countries in Europe, Japan (where he did an opera tour singing Mozart's "Le nozze di Figaro" in November and December 1999) and Israel. He has sung at the La Scala, the Wiener Staatsoper and the Theater an der Wien.