Analyzing Zach Mettenberger's Knee Injury, ACL Rehab Heading into the NFL Draft

Dave Siebert, M.D.@DaveMSiebertFeatured ColumnistMarch 4, 2014

BATON ROUGE, LA - NOVEMBER 29:  Quarterback Zach Mettenberger #8 of the LSU Tigers throws a a pass against the Arkansas Razorbacks at Tiger Stadium on November 29, 2013 in Baton Rouge, Louisiana.  (Photo by Chris Graythen/Getty Images)
Chris Graythen/Getty Images

In late November, former LSU quarterback Zach Mettenberger fell victim to a sprained left ACL and MCL, and the knee injury combo will likely draw concern from NFL teams all the way through the draft in May.

This video from CBS—via Yahoo! Sports—makes clear what happened.

As seen, a hit to the outside portion of the front of Mettenberger's knee sent the quarterback to the ground in pain. Such an injury mechanism is a classic cause of the dreaded ACL/MCL combo.

A hit to the outside of Zach Mettenberger's knee—highlighted by the yellow circle—tore his ACL and MCL.
A hit to the outside of Zach Mettenberger's knee—highlighted by the yellow circle—tore his ACL and MCL.Screenshot from CBS via Yahoo! Sports, with edits by the author

Three months removed from the injury, the former Tiger is well on his way to recovery. In fact, according to Brent Sobleski of USA Today, he was "ahead of schedule" as of early February. As a pocket passer, he may very well retain his potentially elite draft stock if all continues to go well.

Yet the severity of his original injury certainly didn't do him any favors.

Sobleski notes Mettenberger waited over a month for his MCL to heal before undergoing reconstructive ACL surgery:

Mettenberger suffered a torn ACL and a grade three MCL tear Nov. 29. He didn’t have surgery to repair his ACL until Jan. 2. because of the nature of the injury: the MCL was torn completely off the tibia.

“I had to wait for that to heal completely for the doctor’s to go in and fix the ACL,” Mettenberger said in a phone interview. “It makes it a quicker recovery. In the long run the MCL will be stronger from healing itself.”

Video Play Button
Videos you might like

Much of the time, Grade 3 MCL sprains—or complete ligament tears—do not require surgery in and of themselves. Nevertheless, in the case of dual injury, many surgeons will opt to wait for the MCL to heal a significant amount before operating to repair the ACL.

During ACL surgery, an orthopedic surgeon replaces the torn ACL with tissue from elsewhere in the body. In elite athletes, a piece of the patellar tendon—the part of the knee a doctor hits with a reflex hammer—is frequently the tissue of choice.

During the months and years following surgery, the body will cement the replacement ACL "graft" into place within the joint. With time, a fascinating phenomenon known as "ligamentization" transforms the tendon graft into tissue more closely resembling a native ligament.

Unfortunately, the process is a slow and steady one. Furthermore, athletes must not push themselves too hard too soon, or they risk re-injury.

Simply, every rate of rehab progress is unique.

That said, generally speaking, the initial post-operative weeks focus on regaining the knee's range of motion, and basic strength training soon follows. Water or cycling workouts are next, and by two months post-op—where Mettenberger currently sits—some athletes may begin light jogging.

As Mettenberger continues to progress, his physical therapists will soon work in agility drills and lateral motion exercises into his rehab regimen—if they have not already. Side-to-side force adds a new type of stress to a recovering knee, as the healthy ACL serves to prevent the knee from twisting and buckling inward.

For a pocket quarterback, sidestepping comes into play during the five- and seven-step dropback.

If Mettenberger can master lateral movement by LSU's pro day on April 9, he may have an opportunity to throw for NFL scouts.

To Matt Miller—Bleacher Report's NFL draft lead writer—that may be all he needs.

"A first round quarterback before injury, Mettenberger was hurt mostly because it ended a strong season of development in a pro style scheme," Miller explained. "If healthy enough to wow teams with his arm pre-draft, he could easily push for late first round status."

In other words, it may simply come down to NFL squads assuring he is rehabbing as expected.

Assuming no complications or setbacks arise—a reasonably safe assumption given the quality of medical care he is surely receiving—the former LSU signal-caller might one day look at his injury as only a small speed bump on the road to an otherwise-promising NFL career.

Dr. Dave Siebert is a resident physician at the University of Washington who plans to pursue fellowship training in Primary Care (non-operative) Sports Medicine. Quotes were obtained firsthand unless otherwise noted.