Meet the PCL, The Lesser-Known Knee Ligament That's Keeping NFL Players on the Sidelines

Learn about PCL injuries and how elite athletes can play at a high level without this knee ligament.

What do Andre Ellington, Eric Decker, Kyle Williams and Breshad Perriman have in common? Each of these NFL stars has been dealing with a PCL injury in the 2015 NFL season.

You might be wondering, "Wait. What the heck is a PCL? Don't you mean ACL?"

I asked those exact same questions when my doctor told me I had torn my posterior cruciate ligament during a hockey game early in my college career.

An opponent was holding my lower leg and I was checked by another player. I stood up and, in my rage, slashed the perpetrator. After skating over to the penalty box in shame, I lifted my leg to step up into the box. I immediately knew something was wrong. I figured it was nothing major until I tried to take my skate off. The pulling and twisting created an unbearable pain in my knee. The injury ultimately ended my competitive hockey career.

I spoke with Dr. Rocco Monto, an orthopedic surgeon and STACK Expert, to learn more about the PCL.

What is the PCL and How Is It Injured?

What is the PCL and How Is It Injured?

The posterior cruciate ligament is one of four ligaments that stabilize the knee joint while allowing it to bend and slightly twist. Located in the center of the knee just behind the ACL, it attaches from the inside of the femur (i.e., thigh bone) down the back of the knee to the tibia (i.e., shin bone). About as thick as your thumb, it's a strong ligament, which, according to Monto, can handle nearly twice as much force as the ACL.

Whereas the ACL prevents the tibia from sliding forward in relation to the femur, the PCL prevents the tibia from sagging backward. In medical speak, this is called posterior drawer.

The video below shows what a knee with a PCL injury looks like compared to a healthy knee. The knee moves significantly. (Depending on your degree of squeamishness, you may not want to watch the video.)

Monto explains, "It's real important when you're climbing stairs. When the knee is bent and is being pushed back a little bit, that's where the PCL is coming into play. It also plays a role when the knee twists to the outside."

The PCL is a strong ligament, so it takes a lot of force to cause it to rupture. It is typically injured when there's an impact on the shin bone. Monto says it often happens during car accidents when the lower leg is hit by the dashboard. In sports, it  usually occurs during collisions with the lower leg. Monto adds, "Linebackers often have PCL injuries because their opponents hit the front of their lower leg, or they get chop blocked and the tibia shoots back."

The ligament is particularly vulnerable when the knee is at a 90-degree angle. When I started playing hockey again after my recovery, I experienced significant pain any time I fell on my knee when it was bent.

Full tears or ruptures of the PCL are rare. Partial tears are more common—or the bone where the PCL attaches actually breaks because the ligament is so strong.

"It takes a lot to pop a PCL. That's why the incidence is so much lower than an ACL," says Monto.

RELATED: Squat Modifications to Train Around an Injury

Recovering From a PCL Injury

Recovering From a PCL Injury

The first course of action with any knee injury is to go to the ER. There, you'll likely get an X-ray and/or an MRI, and the doctor will perform a series of tests. He'll bend the knee, twist it and pull and push on the tibia. If you have a PCL injury, you'll know it immediately when the doctor pushes down on the tibia. Let's just say it's very uncomfortable.

This test looks for posterior drawer. The amount of posterior drawer indicates the severity of the injury, and it can easily be seen when comparing the injured to the non-injured knee.

From there, it's important to consult with an orthopedic surgeon so he or she can evaluate the severity of the injury and provide a rehab protocol. In my case, the orthopedic surgeon performed specialized x-rays designed to measure the amount of movement within my knee.

Unlike with ACLs, it's not common to have a PCL surgically reconstructed, because it's a tough ligament to repair with current surgical methods. "We've had a lot of trouble restoring the PCL," Monto says. "When we do reconstructions, patients are just not as satisfied compared to ACLs."

This is due to a few factors. First, the repair is typically done through the backside of the knee, which is much more difficult to work through than the front of the knee—where the ACL is accessed. Second, reconstructions are done with a graft from a cadaver, which do not work as well as a graft from your own body. The PCL is simply too long to use a graft from your own body.

Fortunately, you don't need a PCL.

"You don't see terrible long-term side effects with PCL injuries, so the urgency to fix it isn't quite the same as ACLs," explains Monto. "A lot of people live without the PCL or with it damaged."

In general, athletes do well when coming back from a PCL injury. Monto says that about two percent of NFL prospects test positive for PCL injuries at the NFL Combine without it having been an issue. And many players are playing at an extremely high level without a PCL. For example, there are reports that Calvin Johnson had a partial PCL tear in 2013.

"It's not as critical to cutting in sports as the ACL," Monto adds.

Instead of surgery, a non-invasive rehab protocol is usually prescribed. Here, Monto outlines the most up-to-date PCL rehab steps:

  • Initially a knee brace is worn to prevent the knee from bending more than 50 to 60 degrees, which reduces stress on the PCL. You'd also use crutches.

  • Developing quad strength is an immediate focus with exercises such as Leg Extensions. The quads help to pull the lower leg forward, making them critical for an athlete with a PCL injury. Hamstring exercises are avoided because they pull the lower leg backward.

  • Two to three weeks after the injury, you're allowed to walk without crutches, ride an exercise bike and continue developing your quads. Range of motion is still limited.

  • By weeks eight to 10, running is incorporated along with more advanced quad development exercises like Step-Ups. When training, avoid deep Squats and other extreme knee bends.

  • It's possible to return to play after two to three months, which is significantly faster than the year it typically takes to come back from an ACL injury.

  • Once the return to play, athletes wear a carbon fiber knee brace with straps that prevent the tibia from falling backward.

The long-term results of this protocol depend on the individual. Monto says about 80 percent of athletes return to their sport and play at a high level. But it is possible that a PCL injury can slightly impair performance due to instability or lack of confidence in the joint. About 20 percent of the time, athletes are unable to continue playing their sport.

As a young college athlete, I believed my physical therapist wasn't aggressive enough with my treatment, and I wanted to get back on the ice as soon as possible. When I continued to have problems with my PCL, I knew my hasty return was misguided. It ultimately caused me to stop playing competitively.

RELATED: The Best Single-Leg Exercises for Athletes

Living and Competing With a PCL Injury

Andre Ellington

Since college, I've made it a priority to train my lower body with a focus on quad development. This helps keep my tibia from sagging backward and improves stability in the joint. If I tighten my quad, the posterior drawer is minimal.

Although my knee looks very loose (and kind of gross), it does not bother me at all. I play hockey, tennis and work out without problems, all without a knee brace. I continue to avoid Squats deeper than parallel to avoid putting extra stress on my knee.

From personal experience, I advise you to follow your physical therapist's program and recommendations. And when you're done with physical therapy, make sure to restore your strength in the weight room before you return to the field.

Despite what may seem like an excessive amount of movement in the knee, there are few things to be concerned about long-term. "A torn PCL doesn't seem to cause arthritis like the ACL," says Monto.

Again, the key is quad strength. "You want to be like quadzilla," quips Monto. "In fact, you won't want to do a lot of hamstring work to help keep the knee forward."

To keep your quads strong, incorporate these exercises into your workouts.

Band Two-Way Touches

(Shown in the video player above)

  • Wrap a resistance band around your left ankle and attach the opposite end to a fixed position.
  • Stand in a quarter-squat position with your feet hip-width apart and the band to your left.
  • Remove all slack in the band.
  • With all your weight on your right leg, tap your left foot on the ground about 2 feet to the side and again directly under your body.
  • Continue for the specified number of reps and repeat with your left leg.
  • Repeat with the resistance band positioned behind your body.

Sets/Reps: 3x25 each leg, each variation

Dumbbell Step-Up

  • Stand with your feet hip-width apart about 6 inches away from a box.
  • Step onto the box with your right foot.
  • Extend your right leg to drive your body up and place your left foot on the box.
  • Step down from the box and repeat.

Sets/Reps: 2x8-10 each leg

Lateral Step-Up

  • Stand with your feet hip-width apart about 6 inches to the left of a box.
  • Step onto the box with your right foot.
  • Extend your right leg to drive your body up and place your left foot on the box.
  • Step down from the box, and repeat.

Sets/Reps: 2x8-10 each leg

Cross-Over Step-Up

  • Stand with your feet hip-width apart about 6 inches to the left of a box.
  • Step onto the box with your left foot so your thigh crosses your body; keep your knee over your ankle.
  • Extend your left leg to drive your body up, and place your right foot on the box.
  • Step down with your right foot, and repeat.

Sets/Reps: 2x8-10 each leg

RELATED: Test Your Quad Strength With Wall Sits

Photo Credit: Getty Images // Thinkstock