He is most famous for controversially winning the gold medal in men's javelin throw at the 1980 Summer Olympics, becoming the second Latvian to achieve this (after Jānis Lūsis).

[2] However, in front of the home crowd, the officials raised a white flag indicating that the throw was good; it was measured at 88.88, easily enough to advance him to the last three rounds (indeed taking the lead at that point).

The silver went to Aleksandr Makarov with a last-round mark of 89.64, giving the Soviet Union both of the top spots, while Wolfgang Hanisch of East Germany took the bronze medal.

Petranoff, who had thrown a new world record of 99.72 earlier that year, and the eventual winner Detlef Michel of East Germany had been the pre-meet favorites.

In 1988 he was released from the Soviet team, however he continued to compete internationally up until the 1993 World Championships in Athletics in Stuttgart, by then representing his native Latvia.