Dwayne "THE ROCK" JOHNSON is talking about the injuries that have torn up his athlete-turned-movie-star body over the years. A complete shoulder reconstruction. Four knee surgeries. One by one, he ticks off his old football wounds. One, two, three ruptured disks, all during his senior year in college.

"It’s like taking a jelly doughnut and squashing it," says the former World Wrestling Entertainment champion, smacking his hands together, "and all the myelin comes out."

Fortunately, Johnson has a better suggestion for lunch as he talks about his new film, "Gridiron Gang," opening Friday - the backyard patio of Romio’s Pizza and Pasta in Westlake Village, one of Johnson’s regular haunts when he’s in town. (Most of the time he lives in Davie, Fla., with his wife, Danyelle, their 5-year-old daughter, Simone, and their extended family.)

Johnson, 36, survived production of the rough and tumble football film unscathed, but that was hardly a foregone conclusion. The movie is about an intrepid probation officer named Sean Porter who started a football team for violent juvenile offenders at Camp Kilpatrick in Malibu. As Coach Porter, Johnson puts on football pads so that one of his charges can learn how to knock him down by practicing over and over. And over and over.

"Gridiron Gang" is based on Linda and Lee Stanley’s 1993 Emmy Award-winning documentary of the same name, and they signed on as producers for the feature film as well.

A tough nice guy

In his next project, Disney’s "The Game Plan," a father-daughter film in which he plays, you guessed it, a football star, he didn’t fare as well physically. He ripped his left Achilles tendon during rehearsals in June, which elicted two thoughts: First, "This really hurts." Then, "There are a lot of jobs that are now being put on hold."

Work on that film was suspended for the summer a week before production was to start and now Johnson, casually dressed in jeans and a dark-blue polo shirt, is hobbling around on a soft cast while he travels the country promoting "Gridiron." That second thought he had about the welfare of "The Game Plan’s" crew is vintage Johnson, the sense he projects that a heart really does beat behind that muscle-bound breast.

He says he and Porter marvel at how much they have in common. They both have Pacific Island roots (Porter is half Hawaiian, Johnson half Samoan). Both had nurturing mothers and distant fathers. Porter’s mother died on Johnson’s mother’s birthday.

"We went to dinner the other night and he said, ’There’s a reason why you’re here,’ " Johnson says as he tucks into his chicken Caesar salad, light on the dressing. "I believe in that." He stabs leaves of romaine, tattooed biceps the size of babies’ bellies bunching up with each forkful. After his guest teases him about such a girly-man lunch, Johnson orders a plain pizza and the house specialty, a plate of cheese bread with marinara, but he barely touches them.

During the month of filming at Camp Kilpatrick, Johnson was Porter-like even after the cameras stopped rolling. Every week, he visited the inmates in their dorms to give them some of that get-straight, tough-love talk that helped some of Porter’s team of Mustangs beat the odds on the outside.

"At the end of the day, you realize when you’ve spent so much time with these kids that they’re just kids," he says. "They’re well aware that they did wrong. They don’t want to be a screw-up. It’s all they know. When they get out, they go right back into that bad environment. That’s why it’s important to let them know, you’re going to be in your environment, but you’re still going to have a choice."

What producer Neal H. Moritz didn’t know when he sent Johnson the script was that the star had just as much in common with the kids as he did with the coach. As a teen growing up in Hawaii, he was arrested eight times for misdemeanor fighting and theft. Back then, Johnson had his own Sean Porter, a probation officer who persuaded him to channel his adolescent energy into playing on his high school football team. The other "defining moment" that turned him around, as he puts it, came when his mother, already struggling with poverty, got him out of jail when he was 17.

"She was crying in the car and not saying anything," he says. "Between evictions and repossessions and electricity getting shut off, as much crap as my parents were going through, I realized that I was just adding to it. At that point, I said, ’I’ve got to change my life around.’ "

From ring to screen

Still, he seems pretty relaxed about his transformation. "Now it’s so interchangeable," he says. "In ’Southland Tales,’ I’m Dwayne Johnson. If there’s an action movie, it’s the Rock. I just thought in time things would change, and that’s what happened."