A video of the injury, courtesy of CBS—via Yahoo! Sports—offers some insight into what happened.
Admittedly, the pseudo-diagnosis of "chest injury" does not provide much information. That said, the above replay shows a Patriots defender partially drive Moreno's left shoulder and side into the ground—a mechanism of injury consistent with injury possibilities such as a rib contusion, clavicle fracture or sternoclavicular (SC) joint sprain, among others.
Fortunately, after the game, ESPN's Josina Anderson reported Moreno's X-rays came back negative, implying the lack of an obvious rib or clavicle fracture. A very severe SC joint dislocation is also likely off the table.
Source: X-rays done on Broncos RB Knowshon Moreno in the rib area were negative.— Josina Anderson (@JosinaAnderson) January 20, 2014
Nevertheless, an exact prognosis may remain unclear for some time.
While obvious bone misalignment on X-ray can sometimes suggest severe ligament injury, more subtle soft tissue damage generally remains hidden to simple imaging. Doctors may also need to use other radiographic techniques to completely characterize the existence of SC joint damage.
What does that mean for Moreno?
In the best-case scenario, a minor rib contusion only minimally limits the fifth-year running back in practice leading up to the Super Bowl. A slight intercostal muscle strain—or a tear in one of the muscles between the ribs—can also heal in the next two weeks.
Then, if treatment can provide adequate pain control, playing through one of the above mild injuries becomes a very real possibility.
On the other hand, an unstable SC joint—or the area at which the clavicle meets the sternum—is another story. Significant disruption of the ligaments at the joint can allow for motion of one bone about the other, and if the collarbone moves backward, it can press on vital structures within the chest such as the trachea.
Dislocated ribs can pose a similar threat.
In 2012, Pittsburgh Steelers quarterback Ben Roethlisberger missed significant time after an extremely rare dislocated first rib threatened his aorta. Doctors needed to hold him out until the injury fully healed, as if another hit were to move his first rib out of place even further, it could interfere with the aorta's function of supplying blood to the rest of the body.
Who will win Super Bowl XLVII?
Luckily, negative X-rays—as well as the fact that no media reports of serious complications immediately surfaced following the game—suggest Moreno's injury lies on the minor end of the severity spectrum.
Even if a rib fracture somehow escaped X-rays—possible, but less likely—NFL players frequently play through small breaks as long as the ends of the broken rib or ribs do not threaten the lungs or heart. Houston Texans running back Ben Tate played through four broken ribs earlier this season before moving to injured reserve.
With that in mind, barring an as-of-yet unforeseen announcement of a serious SC injury or pectoral muscle tear, ample rest and treatment should allow Moreno to return in time for a Super Bowl XLVIII matchup against the Seattle Seahawks.
Dr. Dave Siebert is a resident physician at the University of Washington. He plans to pursue fellowship training in Primary Care (non-operative) Sports Medicine.