Breaking down Adrian Peterson's injury

Why waste time with an intro? We all know what (and who) everyone is talking about heading into Week 11.

Running Backs

Adrian Peterson, Vikings: Coach Brad Childress announced on Monday afternoon that Peterson suffered a Grade II+ lateral collateral ligament sprain. And everyone was a bit unsure what to make of it. After all, this is not an ordinary, everyday injury. And Peterson has shown that he is not an ordinary, everyday player. All Day? Certainly. Ordinary? Never. Just ask my friend Merril Hoge, who has been singing his praises since the preseason on the "ESPNEWS Fantasy Insider" show. So what are concerned fantasy owners to make of a not-so-ordinary injury happening to an extraordinary player? Let's break it down.

The LCL is one of the four main stabilizing ligaments of the knee, situated on the outer aspect of the joint, and it runs from the far end of the thigh bone (femur) to the near end of the outer bone of the lower leg (fibula). It is opposite the medial collateral ligament, which occupies the same spot on the inner aspect of the knee joint, running from femur to tibia (larger lower leg bone). The main function of the LCL is to protect the knee from excess bowing outward (also called varus stress), or more simply, it helps control lateral stability. It is injured if a bowing or varus force is applied that exceeds what the ligament can handle, typically as a result of direct contact. Peterson told Minneapolis' Star Tribune that he felt a helmet or a shoulder hit his knee and then felt the pain.

It is far less common to sustain an injury to this ligament than to its counterpart, the MCL. The MCL, injured when the knee is forced inward excessively (valgus stress), has already been a source of pain for several key players this year (Brandon Jacobs, Travis Henry and J.P. Losman). There are a few possible reasons for this. First, it is simply more natural to either sustain a blow to the outer knee or cut toward the inside off a plant leg during sports, the two main mechanisms for MCL injury. It is far less common to sustain a blow to the inner knee, the primary mechanism for pure LCL injury. Second, the MCL sits very flat against the joint, so a minor unnatural stress puts it at risk for injury. The LCL has a little more room to tolerate movement because it does not lie flat against the knee. (Fun with biology: it is not really possible to distinguish the MCL by feel, but if you want to feel your own LCL, cross one ankle over the opposite knee, as if making a figure 4, and you can feel a tight ropy band on the outer knee. It is easier to feel because it is not flat against the joint.)

When the LCL is injured in isolation, as reports say is the case with Peterson, the result is instability in the lateral knee, or a decreased tolerance for bowing (varus) stresses. An even bigger concern would be if additional structures that make up the back outside corner of the knee were damaged simultaneously (not the case with Peterson, supposedly); this could mean significantly increased disability and more potential knee joint problems down the line. In the preseason we talked about grades of ligament injuries with Grade I (mild) representing minor injury or overstretching, Grade II (moderate), the most common, representing incomplete tearing, and Grade III (severe) indicating a complete tear or rupture. A Grade II+ LCL injury translates to extensive, but incomplete, ligament damage. Since a portion of the ligament remains intact, surgery is not necessarily indicated. Rehabilitation involves first letting the bruising and swelling settle while immobilizing the knee to let the ligament scar and prevent further injury. The focus then centers on strengthening the muscles (primarily quadriceps and lateral hip muscles) that can provide stability to the lateral aspect of the knee to help compensate for any laxity (looseness) resulting from the ligament damage.

So, now that you know what the injury is, let's get to the questions you really want answered.

  1. How long will Peterson be out?

    This is a tough one to gauge -- which is why Childress did not give a time frame -- because of the infrequent occurrence of this type of injury. You may have heard Childress' comment at his Monday news conference that if this were a lineman, he could be braced and come back and play the next game. But a lineman and an Adrian Peterson are two different species. One of the main challenges Peterson will face that a lineman would not is the need to make sharp directional movements with speed. Stability is critical in order for that to occur. In fact, I asked three orthopedic surgeons, all of whom have worked with professional athletes, what their expectations are for this type of injury with this type of player. Each of them had concern about Peterson returning too soon after such an injury, and each felt that the timetable was hard to judge (note that this was merely medical opinion; none of them examined Peterson). Lateral knee injuries are, in essence, more complex than medial injuries. Given that there has to be enough time to allow ligament healing (which typically takes up to six weeks), followed by strengthening, it is fair to expect Peterson's return to take several weeks. The biggest concern if Peterson returns too soon is that another incident, or even stress on a still unstable knee, could result in more severe damage, which could then translate to chronic problems. On the other hand, he is young and strong and could heal fairly quickly. His progression of activity will be determined on an ongoing basis, depending upon how his knee looks and feels day to day, again making it hard to project a time frame with any certainty. I know, I know. You want to have some idea of how to plan around this situation. For now, assume Peterson is out two weeks at an absolute minimum, with the stronger likelihood being at least four weeks. Don't be surprised if it takes even longer, in which case the Vikings may decide to shut Peterson down for the season.

  2. How will he be affected when he comes back?

    Peterson will be left with some decreased lateral stability in his knee; the ligament is forever altered based on the extent of his injury. However, his ability to compensate for it with muscular support (and he may wear a protective brace as an additional measure) could allow him to return looking like the same running back. Part of this answer depends on how well-healed his injury is when he returns.

  3. Is he at more risk for injury?

    Probably so, especially on the outer part of that right knee. It doesn't mean that he definitely will reinjure it, simply that it won't be as hard to do a second time. This is true for all incomplete ligament injuries however, so it is not terribly unusual. Again, the bigger concern would be that future stresses to this knee may put other stabilizing structures more at risk.

The bottom line is that if you have Adrian Peterson on your fantasy team, you should secure a backup now that you can plan to utilize indefinitely. There is no way of knowing for sure at this point how long Peterson will be out, or if he'll return at all. This may not be what fantasy owners or Vikings fans want to hear. But we have enjoyed his amazing talent for the first half of this season, and we would like to continue to enjoy it for years to come. Let's root for Peterson to come back healthy, even if it means we all have to wait just a little longer.

Larry Johnson, Chiefs: You can take your best cues from the statement issued by the Chiefs on their official Web site Monday. Johnson was listed as out for Week 11, meaning there was no question that he could not play six days later. This early announcement reflects the relative seriousness of the injury. The statement adds that Johnson's swelling continues to decrease and that he will meet with a foot specialist on Nov. 19. In other words, the swelling may be going down, but he needs another week before the specialist can assess his condition. This suggests that the swelling in Johnson's foot continues to prevent the team from having a definitive picture of the injury. We know these midfoot injuries are delicate, and the risk of doing too much too soon can mean the demise of an athlete. There have been murmurings of Johnson potentially having a broken bone in the foot, but that has not been confirmed by the team. As we said last week, swelling can cloud the images that would identify a fracture, so the swelling must subside before accurate pictures can be taken. Rehab right now for Johnson is no doubt focused on minimizing pain and swelling, so that further assessment of his foot can occur. If, in fact, Johnson does have a broken bone, he could miss up to six weeks (or for all intents and purposes, the remainder of the season). If there is no fracture, his return will hinge primarily on how long it takes for the pain and swelling to subside, followed by the time it takes to regain his strength and speed when running, cutting and pushing off. Assume Johnson misses three to four weeks at a minimum, unless there is a fracture, then up the minimum to six weeks from the time of injury.

Reggie Bush, Saints: The only update since Bush injured his head Sunday is that coach Sean Payton told the New Orleans Times-Picayune that he expects Bush to play this week. Bush's stepfather had indicated after Sunday's game that Bush suffered a concussion. The Saints had Tuesday off and return to practice Wednesday, so we will not know Bush's practice status until a bit later.

Marshawn Lynch, Bills: No word yet on the status of Lynch's left ankle. Initial postgame reports on the Bills' official site indicated that X-rays were negative and although Lynch was scheduled for an MRI, those results have not been made public at the time of this posting. It sounds as if Lynch is dealing with a sprain. We will monitor his practice activity throughout the week.

LenDale White, Titans: According to coach Jeff Fisher's comments on the Titans' official Web site, he expects White to practice this week. Not exactly revealing with regard to the nature of White's knee problem, but it does not make the condition sound particularly serious. White is another one to monitor in practice.

Kevin Jones, Lions: Uh-oh. Jones is having pain in his left foot again, yes, the one that had the surgery following his Lisfranc injury last season, the same one that kept him out the first third of this season. Jones had only four carries in Sunday's game and had pain in his foot that kept him out of the second half, according to ESPN's John Clayton. It is not uncommon for Jones to have some postgame soreness, but the fact that he was so limited Sunday is cause for concern. According to The Detroit News, coach Rod Marinelli will limit Jones in practice in an effort to ensure his availability for this week.

DeShaun Foster, Panthers: According to The Charlotte Observer, coach John Fox listed Foster as one of the injured players from Sunday's game. It appears that Foster aggravated the condition in his big toe that was giving him trouble a few weeks ago. Fox indicated that Foster's status was unclear for this week.


Brian Griese, Bears: Griese has what coach Lovie Smith referred to as a left shoulder sprain in his Monday news conference. It does not appear serious.

Vinny Testaverde and David Carr, Panthers: The Rock Hill Herald reports that coach John Fox thinks Carr will be medically cleared to return from his concussion this week. He also stated that Testaverde made it through the Week 10 game "healthy." So who will it be in Week 11? No commitment yet from Fox, so we will watch practice reports to see how things shape up during the week.

Steve McNair, Ravens: This just in. McNair has yet another injury. According to ESPN's John Clayton, McNair has a subluxing left shoulder (meaning it slips slightly out of the joint but doesn't dislocate). No word on when or how this occurred, but the timing is most interesting. Kyle Boller will start this week in his place, officially because McNair is injured, unofficially, well, you have seen the Ravens recently, right?

Wide Receivers/Tight Ends

Isaac Bruce, Rams: Bruce apparently aggravated his hamstring during Sunday's contest against the Saints. The St. Louis Post-Dispatch reports that Bruce may miss a week or two as a result. More catches for Drew Bennett.

James Thrash, Redskins: Although James Thrash was seen on crutches after the game, the Washington Post is reporting that the Redskins say that he sustained a Grade I (mild) high ankle sprain. He is not expected to play this week, but is expected to return in Week 12.

Don't see your player here? Be sure to check back after practice reports when we check in on expected Week 11 returning players Andre Johnson, Laveranues Coles, Deion Branch, David Garrard and many others.