Career
Behnke began playing basketball as a teenager in Pulheim near Cologne. He was recruited by head coach Joe B. Hall to play for the University of Kentucky but became homesick and never appeared in a game for Kentucky. Behnke was drafted by the Cleveland Cavaliers in the 1985 National Basketball Association Draft but remained in Germany.
Behnke played for Turn- und Sportverein Bayer 04 Leverkusen from 1980 through 1992.
From 1992 through 1994 Behnke played for TuS Bramsche. From 1996 through 2000 Behnke played for Telekom Baskets Bonn, with which he twice reached the final of the German championship, losing to his prior team, ALBA Berlin.
Between 1983 and 1995, Behnke made 146 appearances for the German national team, scoring 702 points. He participated in two World Championships and four European Championships and in 1992 competed in the Olympic Games.
In 2000, Behnke retired from basketball.