Even before the dancing starts, there’s something about the way she runs.

Near the beginning of “Little Women,” Saoirse Ronan takes off. Cutting her way through a soberly dressed crowd, she flies across the pavement — blond waves bouncing — her face lit from within by a private smile. Her flapping coat makes it look as though she’s soaring on wings. She’s both of the earth and air; grounded yet light.

The reason Greta Gerwig’s “Little Women” is so fresh and so piercingly alive? Its dancing spirit, in which even a run is a choreographic act.

In this adaptation of Louisa May Alcott’s novel about four sisters growing up in New England during and after the Civil War, Ronan, as the willful Jo, has physical prowess: She’s sharp, she’s spontaneous and she’s more than a little bit wild.

As the close-knit March sisters — Meg, Jo, Beth and Amy — glide and tumble their way through the story, Gerwig orchestrates a kind of choreography that is as much physical as verbal. The actors have a way of bursting through space — and piling on one another, both in love and in anger — so that you’re able to feel their three-dimensional fullness. What Gerwig cultivates visually is choreographic pandemonium: restless, energetic and a hair shy of full-blown chaos.