Robert Griffin III's knee injury is the kind that gives you nightmares, an injury that still leaves a pit in my stomach each time it crosses my mind.

When RG3 went down in a heap while trying to recover a bad snap on Jan. 6, the rookie season of a well-liked, stand-up quarterback and man alike—one who rescued his team from years of ineptitude—was unfairly cut short.

He left the game and did not return, and the Seahawks went on to win the game, eliminating the Redskins from the playoffs.

The video of the injury clearly shows that while Griffin attempted to recover the fumble, his right knee gave way under his body weight.

As it gave out, the knee bent abnormally inward, slightly forward and then backward, a sequence of events that immediately had every athletic trainer and orthopaedic surgeon across the country concerned about his ACL.

After an initial MRI proved inconclusive due to difficulties distinguishing the current injury from previous injuries, the Associated Press reported on Tuesday that an anonymous source close to the situation confirmed an LCL tear.

The source also said that damage to the ACL remained unclear and would be determined during surgery.

However, on Jan. 9, ESPN's Chris Mortensen reported that renowned orthopaedic surgeon and Redskins team physician Dr. James Andrews determined Tuesday night that RG3 did indeed suffer a torn ACL in addition to the torn LCL.

The news of such a devastating injury is heartbreaking, but after review of the replay, it is not terribly surprising.

To understand why that is, let's dust off the old anatomy textbook and review some knee anatomy.

The knee is stabilized by four main ligaments.  They are the following:

• Medial collateral ligament (MCL)
• Lateral collateral ligament (LCL)
• Anterior cruciate ligament (ACL)
• Posterior cruciate ligament (PCL)

Like all ligaments in the human body, each knee ligament is a band of tissue that connects two bones, serving to coordinate and stabilize their motion.

The knee ligaments connect the femur—the thigh bone—to the bones in the lower leg, called the tibia and fibula.

Though similar in that respect, the four ligaments each fill their own unique role.

The MCL runs along the inside of the knee, preventing the knee from bending abnormally inward.  Conversely, the LCL runs along the outside of the knee, preventing the knee from bending abnormally outward.

The ACL and PCL are somewhat different. Generally speaking, they both connect the top, flat end of the tibia—the shin bone—to the bottom, flat end of the femur.

By doing so, the ACL prevents the lower leg from moving forward in relation to the thigh, while the PCL prevents it from moving backward.

In other words, they keep the unbent knee in line with both the lower and upper leg.

Additionally, the ACL assists the MCL in preventing the knee from twisting and moving inward.

When all four knee ligaments are healthy and working together, the knee functions normally, providing stability and balance to the athlete as well as the ability to sprint, cut and change directions quickly.

However, if even one of the four ligaments is injured, an athlete can be severely limited.

A ligament injury, called a "sprain," can be classified as grade-one, grade-two or grade-three.

A grade-one sprain implies merely an over-stretch and no tear. Grade-two and grade-three sprains are partial and complete tears, respectively.

Even grade-one sprains dramatically affect an athlete.

Though not torn, over-stretched ligaments are significantly weaker than normal until they fully heal, resulting in knee instability. Injured ligaments are also significantly more prone to further, more severe injury.

That may be why Griffin has not looked the same since last month, when he suffered a grade-one LCL sprain during a collision with Baltimore Ravens defensive tackle Haloti Ngata.

A strong LCL is crucial for a running quarterback such as RG3, as it prevents the knee from buckling outward when an athlete plants his foot to change directions.

In fact, braces such as the one that Griffin wore on Sunday are designed to assist the LCL by absorbing some of the stress placed on the knee when a player cuts.

While playing on an injured knee ligament, a player may appear slower, more tentative or even in pain, similar to how RG3 looked during the early stages of Sunday's game.

He may also run differently, favor one knee over the other and bear weight in a manner other than to what his knees are accustomed.

That is likely what led up to Griffin going down for the final time on Sunday.

An entire game of favoring his right knee, and thus abnormally stretching and possibly weakning its ligaments, came to a head when his ACL finally paid the price and gave way.

When RG3 stepped back to reach for the fumbled snap on his last play of the night, the weight of his body forced his knee to twist inward more than his ACL could bear, resulting in a tear.

Along with his ACL, his already injured and weak LCL also tore. Simultaneous injury to multiple knee ligaments is quite common given the overlapping nature of each of their functions.

Ligaments—like cartilage and muscle tendons—have extremely poor blood flow when compared to tissues such as muscle fibers and skin. This lack of blood flow prevents them from healing on their own, making surgery necessary for proper repair.

In fact, ACL repair surgeries usually involve removing a piece of tissue from elsewhere in the body—called a "graft"—and using it to serve as a replacement ACL.

According to Mortensen's report, Dr. Andrews likely removed a piece of the patellar tendon—the part of the knee a doctor hits with a reflex hammer—from Griffin's left knee to serve as a new ACL in his right knee.

This is not a new procedure for RG3, as his most recent ACL tear is, in reality, a tear of the graft used to repair a previous ACL tear he suffered in 2009.

As for the LCL, Dr. Andrews either stitched or stapled the torn LCL back together or used a similar graft to replace it, depending on the exact location of the injury.

Following his surgery, Griffin will begin rehab for his ACL and LCL tears. It will involve a steady, stepwise progression from simple weight bearing all the way to running and cutting.

The entire course of rehab could take anywhere from six months to a year, as it takes time for the human body to cement the ACL graft into place.

In other words, RG3 will have to be patient.

He will also have to work at strengthening the muscles around his knee to provide additional support to the joint until the ligaments become stronger.

That said, Mortensen also reports that early projections have Griffin possibly being ready for the 2013 season, which is spectacular news for the Redskins and all NFL fans alike.

Some of that has to do with Dr. Andrews' already impressive track record, one that speaks for itself.  He repaired Adrian Peterson's ACL last year, and not only was AP ready for Week 1 of this season, he came back better than ever, falling just nine yards short of the single-season rushing record.

Hopefully, RG3 can come back just as impressively.

For that to happen, the new ACL graft would need to work itself into his knee just as well as the previous graft did, one that supported Griffin through one of the best rookie seasons in sports history.

Nevertheless, there is no way to predict exactly how RG3 will respond to this new repair, and the addition of an LCL tear significantly complicates his situation.

Yet if there is one player in the NFL that has the willpower and determination to make a triumphant return, it is Griffin.

It is also not just Washington Redskins fans who will be rooting for him.

RG3 electrified the NFL this season, winning the hearts of football fans both young and old and from coast to coast along the way.

It is rare that a player is genuinely liked and supported by the entire fanbase of a professional sport, but Griffin is definitely one of them.

As such, he will certainly have the added motivation of the thoughts and prayers of not just Washington, D.C., but of an entire country throughout his journey.

Though it might seem like an eternity away, RG3 will be back. And after one of the most magical seasons in the history of football, Redskins fans surely can't wait to see him burn opposing defenses once again.

As a football fan who is also in the health care field, neither can I.

Make us proud, Robert.

Dave Siebert is a medical/injury Featured Columnist for Bleacher Report who will graduate from medical school in June. He plans to specialize in both Family Medicine and Primary Care (non-operative) Sports Medicine. Injury and anatomical information discussed above is based on his own knowledge.

Follow @DaveMSiebert