The actress admitted to researching her role as early 1900s hysteria patient Sabina Spielrein for months, a process which shed light on the common psychological diagnosis of the time, hysteria.
"I think it was based on sexuality. You read about the upbringing of women at that time and they had absolutely no idea about the facts of life and what the hell was going on with their bodies when they went through puberty - let alone when they might start to have sexual feelings, what that could be," Knightley explained to The Huffington Post.
"Given the extremely religious nature of a lot of European countries at that time, they were told whatever feelings they might be having was the devil inside them. Sabina didn't know about the facts of life when she first started seeing [Carl] Jung. I think that's where a lot of the hysterical fits came from, and why the Freudian method was so good in treating patients with hysteria."
Knightley went on to say that it was A Dangerous Method screenwriter Christopher Hampton who ultimately encouraged her to learn as much as she could while preparing for the part.
"I did about four months of reading just about as much as I could. I worked with Christopher Hampton before - he wrote the screenplay for Atonement - so as soon as I knew I was going to do the film, I phoned him up and said, 'Help!'" the 26-year-old recalled.
Knightley has said that she enjoyed shooting the psychological drama and had "fun" working with her fellow stars Michael Fassbender and Viggo Mortensen.
A Dangerous Method is released in the UK on February 10.
> Keira Knightley's 'A Dangerous Method' premiere - In pictures
Watch the trailer for A Dangerous Method below: