In the roughly three-minute video released by Bozeman Health, Isom-McDaniel reflected on his near-death encounter with the reportedly 2,000lb (900kg) bison.

"Even though I was on the ground, he could have stomped me, he could have gored me, he could have done anything," he said.

"He wasn't showing aggression or anything like that until it picked a target. That target happened to be me."

Isom-McDaniel said it wasn't the bison ramming into him that caused his injuries, rather, "it was the landing that became the problem".

"It was definitely clear that he had a pretty painful injury," Dr Eric Lowe from Bozeman health said in the video containing Isom-McDaniel's interview.

"You can see some fragments here and there are fractures and break lines right through that," Lowe said, as he pointed to the damaged areas in Isom-McDaniel's X-ray.

The National Park Service says on its website: "Bison may appear tranquil, but these large animals have injured more people in Yellowstone than any other animal."

The organisation advises Yellowstone visitors to remain at least 25 yards (23m) from bison at all times and to "never approach a bison to take a photo".

In footage of the incident, Isom-McDaniel and his grandson appeared to be at a safe distance.

But they likely became targets anyway due to this being the animals mating season, a period where testosterone levels and aggression are heightened, experts say.