Louisville's Kevin Ware on Sunday suffered what may have been the most gruesome sports injury ever televised — and no one knows for sure how it happened.

In the first half of Louisville's game against Duke, Ware broke his tibia when he landed awkwardly trying to block a shot, the bone bursting through the skin. The injury immediately triggered comparisons to Joe Theismann's career-ending fracture thirty years ago on Monday Night Football, which until Sunday was generally considered the most grotesque sports injury to ever air live.

Ware suffered what's known as a compound fracture, a type of "open" fracture in which the broken bone is exposed to air. In Ware's case, the bone apparently split in two places.

Violent breaks of that nature are incredibly rare in sports, especially in lower-contact games like basketball. Here's Robert Glatter writing at Forbes:

Compound or open fractures are typically high-energy type injuries which generally occur when an individual is involved in a high velocity car accident or fall, or when a landing is awkward with twisting or torsional type forces… It is exceedingly rare to see this type of injury in a basketball game, let alone a sports competition in general. [Forbes]

How rare, exactly? Dr. Dave Hnida, medical editor with Denver's CBS affiliate, said he knew of only two things in life that could cause injuries that bad: Car accidents and war.

Given that extreme rarity, there's been much speculation that Ware had a preexisting leg injury that even he may not have known about. It's possible Ware had a stress fracture or fractures — tiny cracks in the bone typically caused by excessive physical activity — that weakened the structural integrity of his tibia, leaving him predisposed to a sudden, severe break.

Two doctors reached by the Associated Press offered that explanation, with one noting that stress fractures of the tibia in particular are common in basketball players. Other medical experts have offered similar speculation, with one telling ABC News that Ware may also have had a vitamin deficiency that either exacerbated the fractures or allowed them to develop in the first place.

Still, weakened bones alone may not be enough to explain why Ware's leg snapped. Though small fractures would leave the bone more prone to a violent break, there'd also need to be an incredible amount of rotational force and bad luck to exploit that weakness so explosively, says CBS' Dr. Hnida.

"Even then, there had to be an odd, yet perfect, combination of a high vertical jump, while moving in a forward position, and landing on a heel with a locked ankle and knee," Hnida said. "Some one in a million torque is the only explanation for an injury like this."

That dovetails with another theory: That the unique court used for the game forced Ware to land dangerously. The game was played on a specially built, elevated court inside a football stadium, meaning there was a sudden drop within feet of the sidelines. As Ware landed, he appeared to twist slightly to avoid plummeting off that edge.

From the Boston Globe's Christopher L. Gasper:

There is no way to know unequivocally if Ware’s injury was caused in part by the elevated court the NCAA uses inside cavernous venues that were meant for football. But it was pretty obvious that Ware tried to stop himself short as he flew out of bounds trying to block a shot. If he didn’t, he could have tumbled off the end of the earth, er, court at Lucas Oil Stadium. [Boston Globe]