Keenan Allen's PCL Tear, Lengthy Recovery Threaten His Once-Elite Draft Stock

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Keenan Allen's PCL Tear, Lengthy Recovery Threaten His Once-Elite Draft Stock
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With the 2013 NFL draft looming in less than two weeks, Keenan Allen's longer-than-expected recovery from a torn posterior cruciate ligament (PCL) continues to weigh heavily on the minds of many draft experts and NFL teams alike.

John David Mercer-USA TODAY Sports
Dr. James Andrews.

According to John Crumpacker of the San Francisco Chronicle, Allen originally suffered the injury toward the end of October during a game against Utah. Renowned orthopedic surgeon Dr. James Andrews later diagnosed Allen with a grade-two PCL tear (h/t Bruce Feldman, CBSSports.com).

While a grade-two PCL tear is certainly a serious injury, it is not the worst-case scenario.

As in Allen's case, surgical reconstruction is often unnecessary for grade-two injuries. Regrettably, however, the wide receiver's unexpectedly long recovery might very well prove to be the final nail in the coffin of his once-surefire first-round potential.

Similar to the anterior cruciate ligament (ACL), the PCL's main function is to keep the lower leg in proper alignment with the thigh. Whereas the ACL prevents the lower leg from moving forward in relation to the thigh, the PCL prevents it from moving backward.

To do its job, the PCL connects the back of the tibia, or shin bone, to the back of the femur—the thigh bone.

When torn, the PCL can no longer prevent the tibia from slipping backward off the femur, and the knee becomes extremely unstable. Sprinting, cutting and even walking can be very difficult—if not impossible—without an intact PCL.

This MRI shows an intact ACL and PCL. The left arrow points to the ACL, and the right arrow the PCL. The tibia (shin bone) can be seen at the bottom of the picture, and the femur (thigh bone) is at the top. The kneecap, not clearly seen, is to the left. Photo from Wikimedia Commons.

Normally, the flat top of the tibia sits slightly forward relative to the back of the femur.

Unfortunately, it is difficult to appreciate the normal position of the tibia by feeling from the outside, as the femur sits deep within the thigh muscles. What's more, the kneecap and patellar tendon—the part of the knee a doctor hits with a reflex hammer—partially cover up where the tibia and femur meet.

While an MRI is an extremely useful tool for gauging the severity of a PCL tear, simple physical exam maneuvers are also helpful.

For instance, with a healthy PCL, an examiner should not be able to push the lower leg of a relaxed patient backward when the knee is bent to 90 degrees.

(WARNING: This clip is not gruesome by any means but does represent abnormal motion at the knee). In this video of a patient with a torn PCL, the "posterior drawer" test is performed. It is positive for PCL injury, as the tibia is easily pushed behind the femur.

On the other hand, a grade-one PCL injury—usually representing a partial ligament tear—permits slight backward motion of the tibia when pushed from the front.

Furthermore, a complete tear allows the lower leg to move backward enough to line up with the back of the femur—defined as grade-two. Finally, if the tibia can be pushed entirely behind the femur, a grade-three injury is diagnosed.

Usually, grade-three injuries are accompanied by damage to other ligaments as well.

Unlike the ACL, the PCL sports remarkable self-healing ability—likely the primary reason Allen and Dr. Andrews elected to forego surgery—and proper rehab helps re-attach itself over a period of several weeks. During that time, exercises to strengthen the quads and hamstrings are crucial in order to take stress off of the healing, weak PCL.

Believe it or not, even grade-three tears are not always treated surgically.

However, injury to other ligaments drastically complicates a PCL's recovery—and often requires surgery in its own right—so doctors usually proceed with surgical reconstruction of the PCL in such a scenario.

With all of that said, Allen's recovery proved less than optimal.

As Feldman reported in February, Allen did not participate in the NFL Scouting Combine due to the injury. Chris Burke of Sports Illustrated wrote this week that Allen originally hoped to work out at the event.

Additionally, on Tuesday, Allen told Matt Barrows of the Sacramento Bee that his knee is still only at "85 percent."

Did the lingering injury affect Allen at his Tuesday pro day? It's hard to say, but it seems possible, as his 40-yard dash time underwhelmed.

Nevertheless, as Matt Miller—Bleacher Report's NFL draft lead writer—discusses, straight-line speed wasn't Allen's strength to begin with:

"It's important to remember that Allen was never a speed player, but excelled because of vision and quickness. His slow recovery time is more of a concern than his poor 40 time to me. He's a late-first, early-second round prospect on my board."

As Miller states, while the 40 time may be somewhat less of an issue, Allen's slow healing time raises some red flags.

First, is his PCL ever going to get back to normal? Fortunately, Dr. Andrews believes it already is and that the problem lies in Allen's still-weak thigh muscles.

Dr. Andrews' assessment is extremely reassuring.

Muscles can be strengthened, but a chronically weak PCL following injury may eventually require surgical reconstruction—a procedure whose recovery could require the greater part of a year.

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Regardless, questions about Allen's knee still swirl.

Though it admittedly represents a bit of a hand-waving way of thinking, the discrepancy between fast and slow healers is a very real one. Whether or not the stubbornness of this injury to heal is due to a one-time, unique setback or a slower innate healing time remains to be seen.

Still, while Allen's slow 40 and injury concerns might take away his first-round potential, his leg strength should completely return well before the start of training camps, and he will surely be drafted early. In fact, it appears all but certain that Allen will walk to the podium before the end of the second draft day—if not much sooner.

 

Dave Siebert is a medical writer for Bleacher Report who will join the University of Washington as a resident physician in June. Medical information discussed above is based on his own knowledge, and quotes were obtained firsthand unless otherwise noted.

Follow Dave on Twitter for more sports, medicine and sports medicine.

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