Steve-O and Johnny Knoxville hospitalised two days into filming 'Jackass 4' after treadmill tuba mishap

Clearly Jackass stars Johnny Knoxville and Steve-O aren't quite as flexible as they used to be.

The daredevil pair have ended up in hospital just two days into filming the comeback Jackass movie, Jackass 4.

Spotted by Cinemablend, co-star and longtime Jackass Bam Margera posted a video update to his own website detailing the amazing mishap, which involves large, brass musical instruments and gym equipment.

Sitting in a hospital waiting room, he explains: “Second day of filming Jackass already, and Steve-O and Knoxville are hospitalised by jumping on a full-speed treadmill, with band equipment.”

He clarifies: “F**kin' tubas.”

Margera adds that he's also at the clinic 'taking a p**s test', though he doesn't mention why, and then shows a few scars of his own on his hands.

Steve-O, real name Stephen Gilchrist Glover, is 46 and Knoxville turned 49 this year.

The movie is being made a full 20 years after the likes of Knoxville, O, Margera and cohorts including Jason 'Wee Man' Acuña, Steve Pontius, Ryan Dunn, Preston Lacy, Dave England and Ehren McGhehey began their odyssey of idiocy for MTV.

The original series, conceived by Knoxville, Jeff Tremaine and Spike Jonze, aired for three seasons on MTV from 2000 to 2002, before expanding its ambitions to the big screen.

The first movie arrived that same year, with Jackass Number Two arriving in 2006 and Jackass 3D emerging in 2010. A spin-off, Jackass presents: Bad Grandpa, with Knoxville reprising his role as calamitous pensioner Irving Zisman, was released in 2013.

Injuries have come thick and fast along the way. Margera has broken ribs, a foot and torn his liver, Steve-O lost a nipple with a BB gun and Knoxville tore his urethra doing a backflip on a bike.

Meanwhile, McGhehey broke his back three times and notched up 25 surgeries.

There has been tragedy amid the laughs too, however.

Ryan Dunn and Zachary Hartwell, a production assistant on Jackass Number Two, died in a car wreck in 2011. Dunn was more than twice the legal limit for alcohol.

As yet, Jackass 4 has no firm release date.

Watch: Steve-O tapes himself to a billboard