I was about to leave home for the office, just before 8 a.m. on Monday, when Mike Greenberg, co-host of ESPN’s “Mike and Mike,” teased that the show would be sharing serious news from the NFL when he and Mike Golic returned at the top of the hour.

When they did, there was ESPN “NFL Insider” Chris Mortensen to intone that Bears tight end Zach Miller was in danger of losing his left leg after suffering a knee dislocation on Sunday during the team’s loss to the Saints.

Rather than rumor mongering, which is exactly what Mortensen and ESPN were engaged in at that moment, they should have had an on-staff medical expert on the air to explain the possibilities because at that point, nobody — including the Bears — could have been absolutely sure what was going on with the status of Miller’s leg. ESPN analyst Stephania Bell, who is a physical therapist, comes to mind.

In my career, I have provided on-field care and/or participated in the after-care of four athletes — one football and three soccer players — following knee dislocations. The first occurred in 1981 when I was a student athletic trainer at Notre Dame. The victim was a Navy football player. I will never forget Notre Dame split end Tony Hunter’s wide-eyed look as he frantically motioned me on the field after delivering the shoulder-high block that caused the injury.

In Miller’s case, his knee wasn’t struck either. He simply landed awkwardly from a jump as he was being simultaneously tackled from above and behind.

Exceedingly rare, a knee dislocation — not to be confused with a dislocated kneecap (patella), which is fairly common — occurs when the joint experiences forces sufficient to disrupt the anatomical relationship between the thigh bone (femur) and the shin bone (tibia).

In such an incident, most — if not all — of the ligament structures between the two bones are torn. So are the tendons.

And if that is all that happens, the victim should be thankful. Yes, thankful, because as bad as those injuries may seem, they do not constitute a true surgical emergency. Once the dislocation is reduced, the damage to those tissues can be fixed later.

In one out of five knee dislocations, however, a true surgical emergency occurs. The popliteal artery in the back of the knee is crushed or torn. If not repaired within 6-8 hours, the injury will eventually result in the amputation of the leg below the knee.

Miller, apparently, was among the one in five and needed an emergency graft by a vascular surgeon to repair his damaged popliteal artery

An ESPN.com story read, “League and team sources told (Mortensen) earlier Monday that surgeons had been working to save Miller’s leg.” No disputing that statement.

However, it went on to read, “(Although) it was not clear whether amputation was ever considered.”

Monday and over the next few days, something so drastic would not be.

The October 1987 issue of the Physician and Sports Medicine documented the cases of 11 individuals with knee dislocations who had popliteal artery tears repaired within eight hours of their injuries. One was a college football player who received model care, having the artery repaired within four hours of the injury. Still, 17 days later, he required amputation. The legs of the other 10 victims were saved.

A literature review in the September 2014 issue of Clinical Orthopaedics and Related Research examined 862 knee dislocations. Of those, 134 had a popliteal artery injury and underwent surgical repair, with 88 percent (112) of those procedures being successful.

Given the Superdome’s proximity to University Medical Center New Orleans and the level of care available there and provided on the field, I would expect Miller to be among the 88 percent.

Still, how does this injury lead to such a drastic result 12 percent of the time? In many other parts of the body, there is a backup blood supply if an artery is occluded. Not so for the popliteal artery.

Essentially, it is the only source of blood for the deep muscles of the lower leg. Robbed of sufficient blood flow for 6-8 hours, the affected muscles die, leading to gangrene and inevitable loss of the limb.

Through it all, the blood supply to the skin may remain uninterrupted.

Precisely for those reasons, the injury can be missed.

Having suffered the dislocation, a victim often has a leg that appears back to normal after the joint is put back in place. Typically, when a major artery is damaged, the skin below the injury site will lose its pink shade and appear more white, blue or purple.

Not necessarily so when the popliteal artery is damaged. The skin can remain pink. Pulses near the ankle remain intact.

Consequently, according to Dr. Harvey Simon, the author of the PSM story, "All patients with a proven or suspected knee dislocation should have arteriogram done on emergency basis."

If the artery is damaged, it should be repaired by a vascular surgeon immediately. Because time is of the essence, that specialist should be contacted even before the arteriogram is obtained, so action can be taken as soon as the results are known.

That Navy football player of 36 years ago? When examined on the field and again in the emergency room, prior to reduction, his pulses below the knee were absent. Almost always, that is a sure sign of popliteal artery damage.

However, the pulses returned after the dislocation was reduced and the arteriogram was negative.

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John Doherty is a certified athletic trainer and licensed physical therapist. This column reflects solely his opinion. Reach him at jdoherty@comhs.org. Follow him on Twitter @JDohertyATCPT.