Karina grew up playing rugby league from a young age and recalls being a disappointed 13 year old girl when there were no longer opportunities for her to play competitively. An extremely driven individual, Karina eventually founded a women's team in 2012 called the Burleigh Bears. Karina was determined to form a Women’s A-Grade team on the Gold Coast to assist in growing the opportunities for females to play at the Senior Club level. She captained the Burleigh Bears for four years, leading them through two premiership victories in 2015 and 2016, this achievement was four years in the making and the Club has since continued to take the title for two more years. To ensure the ongoing development of women’s rugby league in Queensland, Karina and her partner, Vanessa Foliaki decided to leave the Burleigh Bears in 2017 to form another women's side, the Easts Tigers in Brisbane. In 2010, Karina debuted for the Queensland Maroons Rugby League team and has played for the squad in 2012, 2016, 2017 & 2018 as well. On 22 June 2018, Brown captained Queensland in the inaugural Women's State of Origin, scoring her side's only two tries in their 16-10 loss to New South Wales. In 2018, Brown was a part of Australian history when she signed with the Sydney Roosters as one of their 15 marquee player signings. In Round 1 of the 2018 NRL Women's Premiership, Brown made her debut for the Sydney Roosters, starting on the wing in their 10-4 loss to the New Zealand Warriors. In September 2018, Karina competed with the Sydney Roosters in the inaugural NRLW Grand Final against the Brisbane Broncos
International career
In 2013, Karina made her first international debut for the Australian Jillaroos, playing in Game 1 and 3, and was an integral part of the National team's first ever Women's Rugby League World Cup. Karina has consecutively played for the Australian team over the past five years and greatly contributed to the team being the current World Champions. On December 2nd 2017, Karina captained the winning Jillaroos squad in the 2017 World Cup Final against New Zealand with a score of 16-4.