Russell Crowe broke both legs filming 'Robin Hood' - but didn't realise until a decade later.
The 59-year-old actor recalled experiencing a surge of pain when he rushed through filming a scene which required him to jump onto "rock-hard" ground without the surface being properly prepared, but he pressed on with working and didn't realise just how significant the "small mishap" had been until much later.
Speaking to People magazine, Russell - who played the titular outlaw in the 2010 movie - said: "I jumped off a castle portcullis onto rock-hard uneven ground.
We should have prepped the ground and buried a pad but we were in a rush to get the shot done in the fading light.
"With hundreds of extras around, arrows flying and burn pots setting the castle on fire, there was no pulling out. As I jumped, I remember thinking, 'This is going to hurt.' "
The 'Land of Bad' actor aimed to land on the balls of his feet to reduce the impact, but his heels hit the ground first.
He recalled: "It was like an electric shock bursting up through my body.
"We were shooting a big movie, so you just struggle through, but the last month of that job was very tricky. There was a number of weeks where even walking was a challenge."
At the time, Russell "never discussed the injury with production, never took a day off because of it, I just kept going to work."
But a decade later, he sought medical help when he began experiencing "very strange pains" in his lower legs.
He said: "I thought it was nothing serious. After working through a long New York winter, my body was just missing exercise and sunshine."
The Oscar-winning star underwent MRI scans and X-rays and was stunned when the doctor looked at the images and asked when he had broken his legs.
He added: "Apparently he could see the remnants of fractures in both shin bones.
"To jog my memory he said, 'Would have been maybe 10 years ago?' "
Russell immediately remembered the 'Robin Hood' shoot.
He said: "Apparently I finished that movie with two broken legs. All for art. No cast, no splints, no painkillers, just kept going to work and over time they healed themselves."
The 'American Gangster' actor thinks the year off he took between making 'Robin Hood' and 'Man of Steel' helped his recovery.
He said: "In retrospect I obviously knew something was wrong.
"To be the Kryptonian father of Superman was six months of incredibly intense physical training. Between the time off and that training, things fixed themselves."