[1] Sonja Leinamo began her career as a cross-country skier and participated in several Finnish junior and senior championships starting in 2019.
In January 2020, the Finnish athlete competed in the Youth Olympic Games, reaching the quarterfinals in the sprint event and finishing 24th out of 82 starters.
In the following season, the Finn regularly competed at the second-highest level and scored her first ranking points by finishing 23rd in the sprint at Pokljuka.
[3] At the season opener in Östersund, she finished 59th in the individual race and, along with Suvi Minkkinen, Erika Jänkä, and Noora Kaisa Keränen, secured 18th place in the relay.
[4] In the following 2024/2025 season, Sonja Leinamo competed in the relay alongside Suvi Minkkinen, Venla Lehtonen, and Inka Hämäläinen, with the Finnish team securing 8th place.