At the 1957 Boston Marathon, Karvonen was second after John J. Kelley, a young American, who beat Karvonen by almost four minutes. The New York Times reported that midway through the race, Karvonen was clutching his side and seemed to have a stitch. Karvonen was still sixth at the 1958 European Championships with his all-time third best time, 2:22:45, second at the 1958 Fukuoka Marathon, and fourth at the 1959 Boston Marathon. During his career Karvonen ran a total of 35 marathons and won 15 of them.