According to the Houston Chronicle, coach Gary Kubiak indicated Schaub's injury happened during a quarterback sneak. "Somebody fell on the back of his foot, and his foot got caught in the pile," Kubiak said. A force placed on the heel while the athlete's forefoot is fixed firmly on the ground (picture a push-off position with the heel in the air at the time the load is sustained) is the most common mechanism for this type of injury in football. It is often difficult for the athlete to continue to play, and in the most serious situations, it is virtually impossible to bear weight. The surprise with Schaub, who managed to play the majority of the game in spite of the second-quarter injury, came Monday when the team discovered just how significant the injury was. According to the Chronicle, the Texans were "stunned" by the news.Other noteworthy players have suffered Lisfranc injuries -- some severe enough to require surgery -- and have returned to play, although in some cases not to their prior level of play. Running backs Ronnie Brown (injured while a member of the Miami Dolphins in 2009) and Kevin Jones (injured while with the Detroit Lions in 2006) went through lengthy rehabilitation efforts, as did Indianapolis Colts defensive end Dwight Freeney, who was injured in 2007. Although the term "Lisfranc" is more easily recognizable now that several prominent athletes have suffered the injury, what it describes remains a mystery to most. Many have asked on Twitter "What exactly is a Lisfranc?" to which the only response is that the answer deserves more than 140 characters. To help explain the complexity of the injury, along with the origin of its unique name, I returned to an entry I wrote in 2007 when Freeney was recovering from his surgery:So what is this thing they call a Lisfranc injury? There is a region in the middle of the foot where the long bones of the forefoot (metatarsals) articulate with the small tarsal bones in the middle of the foot. This joint is thus called the tarsometatarsal joint. It is also referred to as the Lisfranc joint.Why? Frenchman Jacques Lisfranc, a field surgeon in Napoleon's army, described an amputation technique through this region to address forefoot gangrene following frostbite. There is also the story that soldiers wounded in battle would fall from their horses, but a foot would often remain caught in the stirrup, right at that tarsometatarsal joint. Such an injury often resulted in amputation of part of the foot, from the injured joint forward. In fact, amputation to that region still bears the same name (although NFL players, thankfully, don't need part of their foot amputated when they suffer Lisfranc injuries).Since NFL players aren't riding horses, how does this injury happen to them? There are several mechanisms for this type of injury, but in sports, especially football, the primary scenario is that the player is running forward, with his weight on the ball of his foot, and he gets hit or stepped on from behind against his heel. The resultant force through the portion of the foot in between the ball and the heel (midfoot) causes it to buckle, and the midfoot is injured.Are all Lisfranc injuries the same? No. In fact, the name Lisfranc refers to the region of the foot, not necessarily the severity of the injury. By virtue of its important location (the midfoot essentially forms the arch), any injury to this region needs to be taken seriously. That said, not all Lisfranc injuries are created equal. When the midfoot buckles, the ligaments that connect the various bones can become damaged. Ligament injury without any bony impact would be the mildest version of a Lisfranc injury. The problem is that damage to the ligaments can affect the relative position of the bones in the area, and they can shift or dislocate, which is often accompanied by a fracture. Now it's getting more serious. In the worst-case scenario, an artery passing over that area can also be damaged, affecting blood supply to the foot. A shift of the bony alignment typically requires surgery to realign the joint and provide stability. Failure to do so can result in chronic instability and pain, eventually leading to major arthritis in the area. Even with surgery, it appears that people who have suffered a significant Lisfranc injury are more at risk for arthritis down the road, simply because of the trauma to the joint.The bottom line is that players who suffer these injuries must have their treatment managed carefully, not only with surgery, but in the postsurgical rehabilitation process as well.