A fashion designer and model for Vogue magazine, Knox’s acting career started with a small, uncredited role in Wake Up And Live (1937) but took off with a supporting role in 1940’s Free, Blond And 21. Over her 40 film career, she found herself starring opposite Roy Rodgers in 1941’s Sheriff of Tombstone and the comedy duo of Abbott and Costello in 1943’s Hit The Ice. She played love interest Anne Howe in five of Monogram’s Joe Palooka series entries and was the object of Lon Chaney Jr.’s affections in 1942’s The Mummy’s Tomb.
Knox’s last film was the 1949 musical There’s A Girl In My Heart, after which she left show business in order to raise a family with her husband, 1940 Heisman Trophy winner Tom Harmon. All three of their children Kristy, Kelly and Mark Harmon and granddaughter Tracy Nelson all went into acting.