A Dangerous Method

Rated: R (sex, slapping, spanking, strapping, and language of a mostly psychoanalytic nature)

It’s true that lots of actors go out on a limb. But some limbs are longer than others. The one upon which Keira Knightley finds herself in “A Dangerous Method’’ is as far from the tree as a woman can get without falling to her death. Playing a Jewish Russian mental patient and aspiring psychiatrist named Sabina Spielrein, Knightley gives her entire performance on that limb.

Director David Cronenberg introduces Knightley first convulsing with hysterical laughter as she’s dragged in to meet the Swiss psychiatrist Carl Jung (Michael Fassbender), then alone, a scene later, having a palsied fit. During this introductory nervous attack, Knightley juts out her jaw over and over until it pulls her forward in the chair she grips. It’s as if the jaw wants to run off and find the top half of a pair of chattering windup teeth.

Asking this particular actress to place the emphasis on her jaw, to turn it into something that could pop out of John Hurt’s chest in an “Alien’’ movie or wreak havoc in one of Cronenberg’s early, science fiction films, is a bold opening move. It’s like asking Barbra Streisand to play a bloodhound. Where an actress goes from these opening scenes is surprisingly suspenseful. People have laughed at the immediacy of the movie’s opening minutes, the way Cronenberg puts Knightley’s jaw and Spielrein’s mania front and center. A lot of this movie is conducted as a knowing amusement, but in the risky early minutes, those could only be an audience’s snickers of discomfort. That introduction is a crucial declaration of priorities. “A Dangerous Method’’ begins where other films hope to culminate.

Jung rehabilitates Spielrein from her breakdown using a new, talking style of therapy being developed in Vienna by Sigmund Freud (Viggo Mortensen), who is calling it psychoanalysis. The method proves so beneficial to Spielrein that she overcomes the handicap of her neurosis - something to do with masturbation and her father and being spanked - and becomes the intellectual peer of Jung and Freud, the two more famous men.