According to Joan Niesen and Mike Klis of the The Denver Post, doctors diagnosed Moore with lateral compartment syndrome. He underwent emergency leg surgery to address the issue early Monday morning.
The surgery likely saved his limb, and a closer look at his condition shows why.
Inside the leg and arm, many different muscles control the complex motions of the upper and lower limbs. Tough, minimally stretchable tissue known as fascia binds groups of these muscles into so-called compartments.
For instance, the anterior compartment of the leg contains the muscles around the shin that are responsible for pulling the toes upward. Similarly, the lateral compartment holds those on the outside of the leg that point the toes down and evert the sole of the foot outward.
Compartments also exist within the arms and other areas of the body.
For a better picture, imagine PVC pipes sitting on end within a garbage can. The garbage can represents the circumference of the leg as a whole, and the PVC pipes represent compartments. Inside each pipe sit the aforementioned muscles.
Relatively speaking, fascia can expand more than PVC piping—but not much. As a result, when significant trauma causes fluid to accumulate within a compartment via swelling or bleeding, serious problems can occur due to the rising pressure.
If the amount of accumulating fluid increases the pressure past a critical point, blood cannot flow into the compartment itself.
In other words, the leg cuts off its own blood supply and nerves.
Without blood flow, muscles within the affected compartment can die within a few to several hours. Permanent nerve damage can also result.
Further down the line, dying muscle can induce a process known as rhabdomyolysis as breakdown products reach the blood stream. Rhabdomyolysis can lead to severe kidney damage, among other problems.
Ideally, it never reaches that point.
As mentioned, a quick diagnosis can save a limb from eventual death and amputation, and it seems Moore avoided such a fate.
Yet how did this happen to begin with?
As always, exact medical details are not available to the public. That said, more than likely the Broncos safety sustained a significant blow to the outer portion of his lower leg during Sunday night's game, causing him to leave the field.
Over the next few hours, the pain—rather than subsiding—presumably continued to increase in intensity as tissue swelling progressed, prompting the hospitalization that Niesen and Klis report.
Increased blood flow during exercise can also cause muscles to swell and bring about a chronic, exercise-related compartment syndrome that resolves with rest. More than likely, however, Moore's stemmed from an acute injury.
In the hospital, surgeons likely used a needle to ascertain the pressure within Moore's leg compartments. In addition to clinical findings such as increasing pain or numbness, a pressure above a certain value may signal doctors to proceed to emergency surgery to save the limb.
According to Dr. Adam Bitterman, an orthopedic surgery resident physician based in New York, the procedure involves cutting the fascia itself.
"Treatment of compartment syndrome is done surgically via fasciotomy," Dr. Bitterman explained. "A skin incision is made, with dissection proceeding until the fascial layer is encountered. Using a scalpel blade, the fascia is incised at key points over the muscle compartment."
Relief comes very quickly. Bitterman continued: "Oftentimes an immediate herniation [expansion through the incision] of the tissue will be noted. This muscle release alleviates the pressure, thereby improving blood flow to the tissues."
Recovery times following fasciotomies can vary. For example, compartment syndromes caught early in the process may need less extensive incisions. On the other hand, later stages may produce so much tissue expansion that it becomes impossible to suture the surgical wounds closed until the swelling subsides.
Any additional muscle or nerve damage, if any, further complicates the process, and most surgeries necessitate rehabilitation and strength training to recover lost function.
For now, Moore will focus on recovery, and his exact prognosis will likely become more clear over the coming days.
That said, Niesen and Klis report he will likely miss "several weeks," and a move to injured reserve remains a possibility.
Nevertheless, without the attentiveness of Moore to his developing symptoms—as well as prompt diagnosis and intervention by the Broncos staff—one fact holds true: It could have been much, much worse.
All quotes were obtained firsthand.