Vikings

SEEHAFER: On Zach Miller, Teddy Bridgewater and Dislocated Knees

Knee dislocations are extremely rare, yet extremely serious orthopedic injuries and Monday morning’s report by ESPN’s Adam Schefter that Bears tight end Zach Miller had undergone emergency surgery the night prior in an attempt “to save [his] leg” only serves to highlight that point.

According to ESPN’s Chris Mortenson, Miller suffered a lateral knee dislocation and significant damage to his popliteal artery during Sunday night’s loss to the New Orleans Saints, the latter of which is a dire medical emergency.

The popliteal artery is a continuation of the large femoral artery and runs right through the backside of the knee. It supplies the knee and structures below with blood, and without immediate surgical intervention should it be damaged, amputation becomes a very real possibility. It has been suggested that damage to the popliteal artery can occur in anywhere between 4.8-65 percent of knee dislocations depending on the velocity of the impact that caused the dislocation, however, the estimated overall occurrence is around 19 percent.

Knee dislocations are often classified either by the direction of dislocation or the severity of ligamentous damage. Dislocations can occur in five directions: anteriorly (forward), posteriorly (backward), medially (towards the midline of the body), laterally (away from the midline of the body; “out to the side”) or rotatory (basically diagonally).

Anterior knee dislocations are the most common, accounting for approximately 40 percent of all knee dislocations, with Miller’s lateral dislocation being the second most rare at 11 percent.

Significant ligamentous compromise occurs in nearly all knee dislocations; however, complete disruption of all four of the major knee ligaments – the ACL, PCL, LCL and MCL – is rather rare, with an occurrence rate of only 11 percent. The classification system focusing on the severity of ligament damage can be found below:

1. Robertson A, Nutton RW, Keating JF. Dislocation of the knee. J Bone Joint Surg. 2006; 88: 706-711.

Rupture of the ACL, PCL and either the MCL or the posterolateral corner of the knee capsule — a ligamentous sheath that envelops the knee joint — is the most common injury pattern.

As of right now, it is unknown what specific ligaments Miller damaged with his injury.

Another structure at risk for damage in knee dislocations is the common fibular — also referred to as the common peroneal — nerve. The common fibular nerve splits below the knee into the superficial fibular nerve, which provides sensation to the top of the foot and outside of the lower leg, and the deep fibular nerve, which controls the musculature on the front of the lower leg dorsiflexes (points the toes up while the heel remains on the floor) and everts (pointing the toes outward) the foot.

Damage to the common fibular nerve, which occurs in approximately 20 percent of all knee dislocations, would result in a loss of feeling and “foot drop” (inability to dorsiflex the foot).

At this time it is unknown if Miller received any damage to his common fibular nerve.

Surgical intervention prioritizes the reconstruction of the popliteal artery first, should it be required, followed by the MCL, LCL and the knee capsule. Rebuilding the MCL and/or LCL and the capsule often provides enough stability to allow for a proper healing environment for the compromised popliteal artery. The ACL and PCL are often reconstructed 6-to-12 months later. If surgical intervention is not required on the popliteal artery, the ACL and PCL are addressed 6-to-12 weeks after the MCL, LCL and capsule.

As has been seen with the rehabilitation of Minnesota Vikings quarterback Teddy Bridgewater, returning to play from this significant of an injury takes quite a while. However, the main difference between Miller and Bridgewater’s injuries is that Bridgewater did not experience any arterial or nerve damage, according to the Vikings.

Patients are placed on near non-weight-bearing restrictions and are required to wear a knee immobilizer for up to six weeks after surgery and often return to full weight-bearing by three months. At that point, the patient is progressed cautiously and there is no definitive timeline for returning to play.

It’s been estimated that approximately 19 percent of players who suffered a lower-velocity knee dislocation — often lacking neurovascular compromise — returned to their prior level of sport. However, according to Andrew Heinrichs, it is unlikely that players who suffered a higher-velocity knee dislocation — often involving neurovascular compromise — return to their previous level of competition.

If a player is able to return to their prior level of play, they are at an increased risk of significant knee injuries — both acute and chronic — and have a 50 percent increased risk of developing osteoarthritis.

As stated before, although both players suffered knee dislocations, it’s likely that Miller’s and Bridgewater’s were rather different. It’s unknown what ligamentous structures were ruptured for both players — it’s known that Bridgewater tore his ACL, but that was all that was disclosed — but Miller suffered at least vascular compromise while Bridgewater reportedly did not.

Although both injuries were significant, it just goes to show how “lucky” the Vikings standout quarterback was.

Miller will have a long, grueling recovery ahead of him and at age 33 it would be fair to wonder if it isn’t, unfortunately, career-ending. Of course, that isn’t what matters right now. What matters is Miller’s overall health and well-being. Football is nothing but a game, after all.

As for Bridgewater, who could come off the physically unable to perform list within the next few weeks, the research serves as a cautionary tale. Anybody with a heart and who is a fan of football is pulling for him to return to action and succeed, but getting back on the field, although it would be a major triumph, is only the beginning. He will forever have an elevated risk for suffering another knee injury, not only in his involved knee but also his uninvolved.

It’s imperative that the Vikings and Bridgewater continue to be cautious with his return, putting him back under center only when he and his knee are truly ready, whether that be this season or next.

Academic Sources:

  1. Robertson A, Nutton RW, Keating JF. Dislocation of the knee. J Bone Joint Surg. 2006; 88: 706-711.
  2. Henrichs A. A review of knee dislocations. Journal of Athletic Training. 2004; 39(4): 365-369.

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