Leslie Milne played basketball and hockey (field) at Williams College. She was a member of the US national team from 1978-84, helping the US team win a bronze medal at the 1984 Los Angeles Olympics. In the early 1980s, Milne became close friends with Chris Larson Mason, also a multi-sport star in college, at Penn State, who had also made the US national field hockey team. Milne and Larson Mason began training together in Boston in the mornings, helping maintain their fitness. Milne worked as a photographer during that time to support herself.
After the 1984 Olympics Milne returned to medical school at Temple, and then did her residency and fellowship in emergency medicine at UC San Diego. She became an emergency medicine physician at Mass General Hospital in Boston.