Portman appeared on programme the Late Show with David Letterman on Monday night (22Nov10), revealing the sidesplitting pain she suffered after a lift went wrong.
She said, "I injured a rib, I like dislocated a rib, it sort of went under another one, when you get lifted it just sort of went under."
But there was no one on set to tend to her injury - because the film's budget didn't stretch to include an on-call doctor.
She added: "It's funny because when I got injured I called the producer, I was like 'Could you get the medic? I need an ice pack or something right now,' and he was like, 'Oh, we don't have a medic because it’s super low budget.'
"I have been working for like twenty years, I don't even think that's legal. I was like before you take away a medic, take away my trailer and the next day I didn't have a trailer, I swear to God!"