Knowlden worked steadily in films, many high-budget ones, throughout the 1930s. She was often cast as the daughter of the main characters, or as the leading lady in her childhood. Looking like a younger version of the actress cast as the leading lady was often a major reason why she was cast in a certain role. Unlike most actors, children and adults alike, during the studio system era, she was never contracted to a particular studio. Apart from a temporary period during the filming of "Marie Antoinette" when she studied at Metro-Goldwyn-Mayer's Little Red Schoolhouse, she went to public school instead of schools for child actors in Hollywood. She was in Greta Garbo and Clark Gable's 1931 film "Susan Lenox (Her Fall and Rise)" but her scenes were deleted in the final cut. In 1933, Knowlden had an uncredited role as a young Flora in the pre-code drama "Little Women", which starred Katharine Hepburn, and was nominated for an Academy Award for Best Picture at the 6th Academy Awards in 1934.