Jousts are the medieval sport of choice in A Knight’s Tale, but it takes exactly two measures of the percussive intro to Queen’s arena rouser ”We Will Rock You” – boom boom WAH! boom boom WAH! – to get into the head of Brian Helgeland’s laddish, one joke, genre scrambling rock & roll fairy tale: This is history made smaller than life, Middle Ages pageantry interpreted for stadium spectators with limited attention spans from the age of Whasssup? ads and foam rubber fingers that scream ”We’re Number One!”

In such a setting – a 14th-century Europe populated by dudes and dudettes eager for excellent adventures – socioeconomic realities are a drag for William (Heath Ledger), the lowborn son of a poor thatcher. The working stiff has taught his boy well that a fellow can upgrade his station in life if he’ll Just Do It. (As played by Christopher Cazenove, Pop speaks with the diction of old world England but thinks with the optimism of a new world immigrant American.) Now a young man with the fried platinum hair of a California surfer and the nonthreatening, photogenic looks of a WB contract player (the personable, Australian born Ledger was ogled by the kids while their parents pondered Mel Gibson’s ponytail in ”The Patriot”), William vows to become a knight – the rock star profession of his time. (For emphasis, Queen sings ”gonna be a big man some day,” and the soundtrack wills viewers to be rocked with classic ’70s stuff including Bachman Turner Overdrive’s ”Takin’ Care of Business” and Thin Lizzy’s ”The Boys Are Back in Town.”)

The wannabe nobleman brushes up his jousting skills with the help of rotund, sensitive sidekick Roland (favorite rotund ”Full Monty” alumnus Mark Addy) and hotheaded sidekick Wat (ginger haired Alan Tudyk from ”28 Days”). William christens himself Sir Ulrich von Lichtenstein of Gelderland. Then he fibs himself into a royals only jousting competition with the help of persuasive oratory from Geoff Chaucer (Paul Bettany) – as in the author of ”The Canterbury Tales” – who’s great with gab but a lousy, debt-ridden gambler.

Naturally, William faces an enemy, a snooty count and terrible sport played by Rufus Sewell. (Sewell’s snaky black curls and meanie glower contrast, in cinematic shorthand, with Ledger’s blond, heroic coloring.) Naturally, William falls in love with the same fair lady the count fancies, a mysterious beauty named Jocelyn (newcomer Shannyn Sossamon, who doesn’t so much act as dress up nicely in a striking wardrobe of Japanesey fashion forward ensembles).

And inevitably, with such an Olde Chestnut plot, ”A Knight’s Tale” loses energy even as lances fly. (They fly over the course of a full two hours; audiences are exhorted not to drink bowls of wassail beforehand.) Helgeland, coscreenwriter of ”L.A. Confidential” and director of ”Payback,” may mean ”A Knight’s Tale” to be fun and accessible for those who think ”Monty Python and the Holy Grail” is too darn hip and loony. But for all the jesting and jousting, these are no Python knights who go ”Ni! Ni! Ni!” These are the knights who go ”feh.”