Kari Ristanen made his international début at the 1984 Winter Olympics, where he won a bronze in the relay, but was not as successful in the individual races. Ristanen competed at the 1987 World Championships and 1988 Winter Olympics, but failed to medal in those tournaments, his best individual places at those tournaments being fifth in the 1987 30 km and seventh in the 1988 50 km, which would be Ristanen’s only top ten individual finishes at a major international tournament. Ristanen’s next international tournament medal came at the 1989 World Championships, where he won a silver in the relay, and he made his last international appearance at the 1991 World Championships. By profession Ristanen was an engineer and after his sporting career ended, he has worked as cross-country skiing commentator for Finnish national television. He is married to another cross-country skier Eija Hyytiäinen, who won a relay bronze at the 1984 Olympics.