Answering Questions About Darren Evans' Injury

[Ed. Note: TrueCubbie, a real-life educated doctor-type person who writes for Tomahawk Nation, was kind enough to answer the following questions I had about Darren Evans' knee injury. This post is not meant to slander the Virginia Tech training staff in any way shape or form. These are simply questions about the circumstances surrounding Evans' injury I had and that came up in the comments section of a couple of posts on this blog. TrueCubbie was kind enough to oblige with his opinion as an educated doctor-type person.]

First, thanks to furrer4heisman for the opportunity to write this piece. The management of sports injuries, or illnesses in general, is always easier in hindsight. It's easy to criticize when information is provided to you in an organized, non-real time manner. The decision making in sports injuries has the added complexity of various interests groups and is scrutinized heavily based on those interests. The phrase "Are you hurt? Or, are you injured?" is used all too common. Plus, a dedicated committed player wants to stay on the field, they want to practice, they want to make it to the next level. Playing through pain is the reality of elite competition.

Before continuing, I would recommend reading the piece I wrote about ACL Injuries on our site, Tomahawk Nation. Knee injuries are exceedingly common in college football. Fortunately, the repair and management of such injuries is usually successful due to the fact that they are so common.

Here is the background info that furrer4heisman provided me for the piece and his questions follow:

Some background info: Evans originally hurt his left knee Friday when he stepped on a defensive player's foot. He heard his knee pop and was examined by the team's medical staff. They didn't feel any ligaments out of place and said that he sprained the cartilage around the knee. He didn't participate in contract drills through Monday. On Tuesday, he tore the ACL when he planted his left leg while running a route and went down.

VT's running backs coach said Tuesday he thought Evans must have torn the ACL on Friday. He said because Evans is "so strong nothing was loose in his knee" so the team doctors must not have noticed it.

Questions:

Obviously there is nothing Tech could have done if he tore the ACL on Friday. But why wouldn't they at least do a precautionary MRI if they thought it was a bad sprain? Is it SOP to not do an MRI unless there's "something loose" in the knee?

Diagnosing a knee sprain on exam can be difficult. Feeling any laxity in a joint the size of the knee can be difficult, especially if there is any swelling within the joint that could mask subtle physical exam findings. Significant swelling within the joint occurs within a few hours of an ACL injury. Other injuries typically take time to swell. That swelling, isn't necessarily apparent on inspection of the knee. The fluid is collecting within the joint space which is a closed cavity and is of limited space. Plus, who knows how much pain Evans reporting? There may have been an initial amount of pain that decreased to a tolerable amount and he under reported his symptoms. Therefore, if the exam was not conclusive, meaning there was no evidence of ligamentous laxity, and his pain was reported as minimal, an MRI may not have been warranted at that time. There are various clinical pathways and algorithms to determine when an MRI is indicated. Not all knee injuries require and MRI. It depends on the clinical scenario, the mechanism of injury and the physical exam. One could get into the ethical debate about high performance athletes and the needs for immediate diagnostic testing and evaluation given the larger stakes involved, but I am not going to get into that discussion. Medical resources are limited. An MRI costs a few thousand dollars when you include the fee for the exam and for the interpretation of the images. Thousands of images are obtained during a scan. The decision to obtain the MRI is up to the examining physician, whose judgement will depend on his or her training and experience. Knowing the end result, it's easy to say an MRI should have been done, but only the teams docs know what his exam showed.

Could Tuesday have been too early for Evans to return to contact drills? Could the injury Friday have weakened the ACL to make it more susceptible to a tear? Would the cartilage around the knee being sprained make his more vulnerable to a tear?

Again, it's easy to look back and say, "He should have sat out longer." Could the injury he experienced on Friday have been a partial tear of his ACL? Absolutely. Would this set it up for a tear? Yes. If he sprained one of the ligaments around his knee, he may have been trying to compensate for the injury and put himself in a position to injure it. Or, if there was ligamentous laxity from a ligament injury, it may have made him more susceptible for an ACL injury. There is a common 'triad' of injuries that is seen quite frequently: Medial Colateral tear, ACL tear and meniscus injury. This type of injury results when a foot is planted and a force is applied to the side of the knee, pushing it in. Imagine a running back with his foot planted and a tackler coming in from the side and making contact with the knee. Depending on Evans's symptoms, pain and physical exam, he may have been cleared to return to practice. Hard to say without actually being there.

Is Hite right that Evans' strength could have hidden a torn ACL? If he had actually torn it, wouldn't it have been obvious enough to the medical staff that they would have ordered an MRI?

As I mentioned above, fluid (typically blood) quickly collects within the joint within hours that could provide the sense of stability of the knee. The fluid in the joint makes it seem more stable than it actually is. This is an example of the Anterior Drawer test, which is one of the commonly used exams to identify a torn ACL. Another physical exam skill to identify an ACL tear is th Lachman Test. Here is a video of a patient who does have an ACL tear. Notice the size of the patient; she is tiny. Imagine trying to perform those exams on someone like Evans; it's difficult. With a good history of the injury and a good physical exam, an ACL injury can be diagnosed clinically. The Lachman Test has a sensitivity of 86% and a specificity of 91%. The Anterior drawer test has a sensitivity and specificity of 20% and 88%. The pivot test has a sensitivity and specificity of 18-48% and 97-99%. For an explanation of sensitivity and specificity, go here. That explanation is pretty good and should give you some sense of what these numbers mean if you are not familiar with them. In a nutshell, a positive result in the pivot test is good for saying there is an ACL rupture and a negative result in the Lachman is good for saying there is not a rupture. If you had one test to say yes or no, it would be the Lachman. So, if the Lachman was negative and the pivot test was negative, the likelihood of an ACL tear being present is low. Again, imagine trying to perform those tests in a very muscular person. His muscle bulk alone would make it difficult and depending how relaxed he was for the exam, the exam could have been unremarkable. 

Hope this was helpful in your understanding of ACL injuries and what may or may not have happened in the days leading up to Evans's injury.

Cheers,

TC

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