Sirkka Polkunen made her international début at the 1952 Olympic Winter Games, where she was fifth in the 10 km. At the 1954 World Championships Polkunen won silver in the relay and was sixth in 10 km. At the 1956 Winter Olympics Polkunen won gold as a member of the Finnish relay team and finished eighth in the 10 km. Domestically Polkunen never won a Finnish title, but was second at 10 km in 1954 and won bronzes over 10 km in 1951, 1953 and 1956. She also won the 10 km race at Zakopane in 1955 and was second in 1952 and won bronzes in 1953 and 1955 in the 10 km at the Lahti Ski Games. During and after her sporting career Polkunen worked as a loader and packer at the Vihtavuori gunpowder factory.