Representing East Germany, he was a finalist in men's 800 metres at the 1980 Summer Olympics and the 1982 European Championships and placed third at the 1981 IAAF World Cup.

At the 1977 European Junior Championships in Donetsk, Wagenknecht won gold in the 4 × 400 m relay (as part of the East German team) and silver in the individual 800 m (behind his teammate Andreas Busse).

[9][10] In 1982, Wagenknecht won his third national title, ahead of Beyer; at the European Championships in Athens he placed sixth.

[10] In 1983 he was national champion both indoors and outdoors, but was eliminated in the semi-finals at the inaugural Athletics World Championships in Helsinki; he stayed with the leading group until the end, but was outkicked.

[4][11][12] Wagenknecht won his final East German titles in 1984, repeating as indoor and outdoor champion.