Hamstring Injuries Continue to Plague NFL

The hamstring injury bug continues to bite the NFL. The most significant victims include Philadelphia Eagles quarterback Michael Vick, Arizona Cardinals wide receiver Larry Fitzgerald and Atlanta Falcons offensive stars Roddy White and Steven Jackson.

Vick suffered his injury on Oct. 6 and underwent an MRI the next day, revealing the strain. White went down with his own on Monday Night Football later that evening. The two joined a group that already included Jackson—an injury he suffered in the middle of last month—and Fitzgerald, whose troubles also stem back to early September.

Unfortunately, owing to the nature of the injury itself, hamstring strains tend to linger, resurface and recur. As such, the above injuries may make themselves known for some time still.

Hamstring Anatomy and Injury Mechanism

Before looking at each individual injury, let's crack open the anatomy textbooks for a quick review.

The hamstring is actually a group of three muscles—the semimembranosus, semitendinosus and biceps femoris—that connects the pelvis to the lower leg just below the knee. The three work in tandem to bend the knee and extend the hip—or swing the leg backward behind the body.

When full-speed sprinting or some other force over-stretches one or more hamstring muscles, a strain results.

Grade-one strains are mere over-stretches with microscopic muscle tearing, while grade-two and grade-three strains are partial and complete muscle tears, respectively.

Strains usually occur during mid-stride. Specifically, the hamstring reaches its maximum length at the end of the forward-leg-swing phase of running, immediately before contracting to pull the leg underneath the body.

In other words, while running, the hamstring muscles go through repeated cycles of forceful stretching and shortening. If an athlete overuses them—or uses them without properly warming up—injuries can result.

After a strain sets in, further complications may also loom.

For one, it's very difficult to fully rest the hamstring. Using an injured hamstring also places it at higher risk of worse injury.

Furthermore, a prior hamstring strain is one of the biggest risk factors for another injury further down the line.

Michael Vick's Injury: How Bad Is It?

As mentioned, Vick sustained his injury during Week 5. According to Geoff Mosher of CSN Philly, he'll remain out at least through Week 7—the two-week mark.

Reuben Frank—also of CSN Philly—reports that the injury is worse than expected.

"It’s worse than what I thought it was going to be,” Vick said. “It’s just slow. It’s taking longer than I thought it would."

Frank goes on to discuss the location of the injury, stating that the injury is "high."

In other words, the muscle tear is closer to the hip rather than the knee, or "proximal." Proximal injuries usually require more time to heal.

As Vick's strain will surpass two weeks of missed time this Sunday, it's likely the Eagles quarterback sustained either a serious grade-one or grade-two injury.

While grade-ones usually lead to somewhere between zero and two weeks of missed time, grade-twos can eclipse four or more.

Even worse, it's all too easy to aggravate a hamstring injury—think Jordy Nelson last year—especially as a running quarterback, so the story may regrettably be far from over. With Nick Foles shining in Vick's absence, the strain may even end up defining the future of the Eagles offense.

Roddy White's Injury: Is It Related to His Ankle?

White is no stranger to injuries this season. He suffered a high-ankle sprain in the preseason, and speculation suggests his hamstring strain is related.

For instance, it's possible the ankle sprain affected his gait. If so, the abnormal strides possibly stressed the hamstring in a way to which it is not accustomed.

In such a scenario, the hamstring wears down until one large hit or stride causes it to give way.

Admittedly, the above sequence of events represents mere speculation; exact medical details are not available.

That said, according to ESPN's Adam Schefter, the injury could keep White out for multiple weeks.

Such a timeline suggests a severe grade-one or grade-two injury—similar to Vick.

Fortunately, grade-one and two strains heal on their own—eventually. The hamstring's healing process must simply move faster than the rate of stress placed on it.

Steven Jackson's Injury: Lingering On

According to D. Orlando Ledbetter of the Atlanta Journal-Constitution, Jackson's injury continues to persist a month after the original injury.

Sometimes, that's just the way it goes—especially with running backs.

When a back like Jackson touches the ball, he frequently tries to move at full speed, thereby placing incredible demands on his legs.

An injured hamstring is also less able to resist the types of motions that caused the strain in the first place.

Nevertheless, Jackson's hammy will also heal by itself, as this isn't a grade-three strain, which would require surgery to reattach the muscle.

In fact, for the third time in this article, it's likely Jackson's particular injury is either a grade-two strain or a severe grade-one strain that he has aggravated over the past month.

Larry Fitzgerald's Injury: Feeling the Effects

Fitzgerald continues to play through his hamstring troubles, but he is not playing at a Fitzgerald-like level.

That's likely at least partially related to his injuries.

Low-grade hamstring strains often manifest themselves as a shorter stride on the injured side as well as a lower overall speed—not something an elite wide receiver needs.

After a Thursday night game in Week 7, Fitz will use the following 10 days to rest up his ailing legs before Week 8.

Hopefully, the injury is no worse than a grade-one strain. If so, he may make it over the hump before his next game.

Dr. Dave Siebert is a resident physician at the University of Washington. Find more of his work at the Under the Knife blog.

Follow @DaveMSiebert