A four-time winner of the Ronde van Nederland, he also rode the Tour de France 11 times between 1974 and 1987, winning 10 stages, a Dutch record equalled only by Jan Raas and Joop Zoetemelk. Knetemann won 127 races as a professional.
Knetemann maintained an Amsterdam accent and a sharp sense of humour that made him a favourite with reporters and earned him television and radio appearances. His best year in the Tour de France was 1978, when he led from the sixth stage. Although he lost the leader's yellow jersey two days later, he won the stage into Lausanne and then the final stage on the Champs Elysées in Paris.
Together with Raas and his TI-Raleigh teammates Knetemann played a pivotal role in the victory of Zoetemelk in the 1980 Tour de France, one of the most dominating team performances in Tour de France history in which the team won twelve stages.
Recovery took months and, although he did again ride the Tour de France, there was not much left of the once sparkling star. Knetemann did however win the Amstel Gold Race in 1985. He retired from racing in 1991 and became Dutch team selector.
Knetemann died while riding his bike. He collapsed from a heart attack with friends in De Schoorlse Duinen in Schoorl (gem. Bergen)
His wife, Gre Donker, was also a racing cyclist. They had a son and two daughters. Their daughter Roxane, born in 1987, was a professional cyclist as well.