Why do filmmakers continue to operate under the mistaken assumption that the stories of rock groups that dissolve into misery and tragedy will make good movies? The latest example of why they don’t is provided by this docudrama about the first all-girls’ outfit, which included guitarist Joan Jett and had a meteoric rise before flaming out after a few years. The narrative may be true—or mostly so—but it’s certainly not much fun to watch, especially since the compression of a four-year period into a 100-minute movie doesn’t leave much room for nuance or character development.

The two most prominent members of the band, in Flora Sigismondi’s telling at least, were Jett, one of the co-founders along with drummer Sandy West (Stella Maeve), played by Kristen Stewart of “Twilight” fame, and blonde lead singer Cherie Currie (Dakota Fanning). But there’s a third very important person in Kim Fowley (Michael Shannon), the wild-eyed, histrionic self-styled genius producer/promoter who was instrumental in putting the girls together and fashioning their hard-rock style. The treatment follows the conventional pattern. First comes the difficult formation of the group in 1975, with the addition of Lita Ford (Scout Taylor-Compton) and particular emphasis on the hiring of Currie, a fifteen-year old bombshell whose look Fowley saw as perfect but whose straight-laced attitude needed some adjusting. There follows a section on the group’s early tours under lamentable conditions (exaggerated by Fowley’s miserly ways) and their enjoyment of the various opportunities, sexual and pharmaceutical, that their growing popularity afforded. The intensity of the fan reaction during a visit to Japan shocked the girls.

By that time, however, fissures have already sprung up within the band, especially as Currie goes off the rails and becomes a prima donna in every sense, and eventually everything simply falls apart, with Jett ultimately going her own way while continuing to perform some of the group’s songs. And a would-be poignant coda shows a long-distance reunion between the successful singer and the cleaned-up Currie during a radio call-in show.

This isn’t a dull story, but it’s hardly an unfamiliar one, following the rags-to-riches-to-rags template of so many showbiz tales. And it’s not helped by Sigismondi, whose script opts for the floridly melodramatic and whose direction often seems ragged. (Of course, the visually abrasive cinematography of Benoit Debie and Richard Chew’s brusque editing are contributing factors.)

As to the performances, Stewart rouses herself from her “Twilight” doldrums as Jett (who, as executive producer, must have assured a favorable depiction), and Fanning captures the mixture of bravado and vulnerability that seems to have marked the unhappy Currie, who’s saddled (like most of the others) with family problems. But the person you’re likely to remember best is Shannon, who goes happily over the top in portraying Fowley. The real fellow apparently was (or more properly is) pretty outrageous, but Shannon probably outdoes the real article.

Those interested in a slice of this particular era in rock history will probably find “The Runaways” interesting, if not terribly enlightening. But to those whose tastes run in other directions, the film will instead seem an intriguing but flawed attempt to dramatize the rise and fall of a group that’s more than an historical footnote but less than a household name.