ABC News' Matt Knox and Jen Pereira report:
A newly-released, behind-the-scenes video shows Depp in action on the set, along with the incident that sent the crew rushing to his aid.
The actor was doing his own stunt, galloping on the horse alongside co-star Armie Hammer, who plays the title character in the Disney film (The Walt Disney Co. owns ABC News).
Depp gallops, then slowly starts sliding to the side, eventually falling off the horse and onto the ground. The actor narrowly escapes being crushed by the horse, but he is clipped in the chest by the animal's rear hooves.
Members of the crew run to help him, while cautioning others, except for emergency medical personnel, to stay back.
But Depp was fine. He pulled up his shirt to show bruises on his chest, then quipped: "I'll tell you what the positive thing is. My coccyx [tailbone] didn't take it."
In an appearance on "The Late Show With David Letterman," Depp, who turned 50 earlier this month, recalled the moment when he fell.
"All I saw, in front of my eyes were these very muscular horse legs, the striations of muscles moving, this kind of death machine. One word popped into my head: 'hooves,'" he said.
Depp is not the only star to have faced danger on the set.
Actress Kristin Chenoweth was hit in the head last year by falling lighting equipment while filming a scene for "The Good Wife," a CBS TV drama.
The actress was knocked unconscious, and left the show to fully recover from her injuries. She told The Hollywood Reporter in March that she was still not fully healed, adding that she had sustained a fractured skull, along with rib, tooth and nose damage.
Gerard Butler said he nearly drowned while shooting the film "Chasing Mavericks."
Speaking about the experience in an appearance on "Good Morning America" in October, Butler said, " I was down for a long time, turning, turning and then the next wave came over and I started to think, 'Wow, I'm going to die making a movie.'"
Angelina Jolie cut her head while filming a stunt for her 2010 spy thriller "Salt."
The actress was checked at the hospital before being allowed to resume filming.