IN NEW YORK Now that womenswear is on display, Fashion Week's runways are populated by Giacomettis come to life.

Many of the models are abstractions of the female form, all exaggerated lines and angles. Jutting hipbones atop praying-mantis legs, thin and sharp. The tender fabrics of the fall 2011 fashions can take on hard edges when worn by the average runway model here.

But not when Karlie Kloss stalks the catwalk. She has a way of moving - at once soft and powerful - that goes beyond simple locomotion. Think of the breaking surf, swallows in flight, breezes through palm trees. On Monday, in a turquoise and amethyst silk faille gown by Carolina Herrera, the six-foot-tall Kloss prompted thoughts of the Cutty Sark, with the silk billowing in her wake as she sailed down the runway.

Still in her teens, this focal point of Fashion Week eased up just as she approached the bank of cameras dead ahead; she stopped and took in their zooms with hungry eyes and a roll of her shoulders that echoed down into her liquid hips. Then - and this is what the photographers love about her - she gave them another shot to snap, keeping her gaze focused on the cameras even as she started to make her U-turn.

Like a ballerina riveted to her visual point of reference in a pirouette, Kloss's eyes lingered on the cameras before she turned her head to look where she was going, up the other side of the runway and finally drifting out of sight.

"I love the way she shows," Herrera gushes backstage. "She moves like a cat. I love the way she walks. For me, it's more important than beauty."

Herrera is not alone. Fashion designers appreciate movement and energy, whether in fabric or flesh. Kloss, 18, studied ballet before becoming a model, and her sensuous walk and dramatic stage presence are highly prized. In addition to walking in shows this week, she is featured in a new ad campaign for Christian Dior, for whom the high school senior has modeled for the past three years. (She splits her time between New York and school in her native St. Louis.)

"She embodies for me everything that is about a woman," says designer Donna Karan after her Monday show, in which Kloss wore the last outfit, the most coveted spot for a runway model. It was a viscose satin jersey gown in pale gray. Through sheer corporal emphasis, Kloss turned the ensemble into a neon sign; it might as well have been flashing "Look Look Look."

Photographers are also in her fan club. "She gives us more time to take the picture," says Karl Prouse of the International Herald Tribune. He wants to say more, but "you couldn't print it." So he offers this: "She swings her hips like nobody else." Wink! (A sexy runway model is rare indeed.)

The object of all this praise has a tissue clamped against her cheek by a makeup artist who is tracing eyeliner around one green eye. Kloss, wearing jeans, motorcycle boots and a black leather jacket, is backstage before the start of the Herrera show.

She's one of dozens of models in a huge tent at Lincoln Center who are being fussed over by people wielding hair spray and brushes with the sober intensity of neurosurgeons. Behind them, tables are piled high with muffins and croissants, in which only photographers and reporters show an interest.

A ballet beginning

Kloss deflects compliments about her walk: "I'm not graceful. I'm one of those tall, lanky, awkward kids," she says with a laugh and a megawatt flash of teeth. Her tipped-up eyebrows give her an adorable elfin look, even with her height. She has a simple answer to her rapid rise in modeling, from Missouri at age 13 to photo shoots and runways around the world.

"Ballet single-handedly is the reason why I'm here," she says. Her slender wrists and long manicured fingers wave in the air as she speaks, as if they remember the stage. "My ballet training was honestly the most valuable thing I could've done to prepare myself for this career."

Modeling, Kloss says, "is about movement, about rhythm, about your body and your muscles. Ballet really taught me so much about the power of movement."

Kloss credits dance training with helping her in photos as well as on the runway, "to bring life to the clothes. . . . It's incredibly important in photos, where you're trying to give a three-dimensional feeling. And on the runway, it's so important to embody the feeling of the collection, the energy and feel of the clothes and the inspiration of the designer. That's part of our job, to portray it through our emotions and through our movement."

Orlando Pita, hair designer for the show, swings by to inspect the bun that's been pinned at the nape of Kloss's long neck. Could be neater, he pronounces. "Karlie's one of the most inspiring models I've worked with in 27 years," Pita says while re-coiffing her dark blond hair. "She gets it. The job of a model is to transform, and she's the great transformer."

Many models, he says, "think you just put on a dress and heels and makeup and you go on. You've seen the walk - they parody a model. It's kind of embarrassing. It takes someone very astute to figure out how to look comfortable, how to look appealing to different people. And Karlie's got that."

There are other lovely models in the shows, but alongside Kloss, none conveys the same power. Some models' ways of getting down the runway belong in a Monty Python skit of funny walks; the hips push forward while the arms are crooked back. But even those who are more pleasingly upright lack Kloss's sultry sense of purpose.

What makes Kloss stand out on the runway is not just her ease of movement, but the mood she projects. No bored stare here, no I-could-care-less dust-off. Kloss has a knowingness in her eye as she strides forth; she tucks her chin slightly so the light dances off her cheekbones, and she aims for the flashbulbs with the focus of a panther on the prowl.

A pirouette into modeling

Kloss studied ballet as a child, took a couple of years off for sports, then saw the ballet movie "Center Stage" (which, she notes, takes place at Lincoln Center) and fell back in love with dance. Ballet helped her manage her height.

"I grew six inches in a year," she says with a laugh. "I'm a giant, even in this land of tall people." And since few boys were taking ballet in St. Louis, and none was tall enough to partner with her, she always danced solos, in "Coppelia" and "The Nutcracker."

Kloss was discovered at a model search held in a St. Louis shopping mall. "She was a baby," says Mary Clark, one of her agents. "But she had that walk. We didn't want to change a thing." Her looks and moves were deemed ideal. But so, too, is the way she moves through life. In this temperamental world of nervous frenzy, Kloss's gracious personality is praised as much as her looks.

"She has the sweetest, most delicious heart," Karan says.

But Kloss did have to change one thing. She had to force her feet not to "turn out," or point outward, as they must in ballet. Walking in super-high heels was also difficult, but the dancer's strength in her arches and legs helps.

Dancers are particular about their floors, and runway surfaces aren't at all shock-absorbing. But Kloss says she'd rather walk on the plain old concrete of some of the smaller shows than on the glossy plastic or glass she encounters in the high-concept ones. In Jason Wu's show last week, she had to walk on a mirrored surface in a trailing black silk chiffon gown with gold leaf embroidery. Balance was key.

Her greatest fear is doing "a banana-peel split in front of all the cameras and the whole world."

"Oh yeah, it's common," she says. It hasn't happened to her. Yet.

"But it's not the end of the world. It's all about how gracefully and calmly you collect yourself," she says, as her hands dance through the air again. "The show must go on."

'Dancing down the runway'

Kloss burns to move more; she is like a Maserati under a speed limit. Watching the magnetism and sex appeal she delivers on the runway, you think about the days when models gave more of a performance. When they sauntered and truly sold the clothes, shrugging open their jackets, pivoting and vamping and showing off linings.

"I miss that," laments jewelry designer Gerard Yosca, a longtime fashion follower. "Now it's an absence of expression. It's about a frozen look that moves down the runway. The designers are looking for that one shot that sells the clothes to the retailers. But you want human. You want a sense that there's someone there."

Kloss agrees. "Subconsciously, I wish I lived in the '70s," she says after the show, heading to a taxi while photographers follow her every step. (They have to run to keep up with her walk.) "Oh my gosh, I watch videos from the '70s and '80s and '90s - all the supermodels, Christy Turlington, Linda Evangelista, Kate Moss. These girls used to really walk on the catwalk. It was a performance. There was even more energy, even more drama, even more passion.

"We're going through a phase where it's not really boring but . . . it's a different ballgame, especially on the catwalks," Kloss continues. "I really wish I would have lived in that time when they really went for it, instead of a boring sort of zoned-out, zombielike walk. It was like you were dancing down the runway."

Maybe she'll inspire a resurgence of that kind of women's movement. Of body-conscious models who move with grace, control and pizazz.

"I love that high you get when you're performing. I was so passionate about it: that energy onstage, that rush of adrenaline," she says. "That's the same energy I experience when I'm on the catwalk. I think I'm kind of addicted to it."