Knee Hyperextension and a Deep Breath

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Your friendly musculoskeletal specialist just can’t help himself! He is once again ready to endure criticism for speculating on an injury to one of our beloved Royals. (Full disclosure: Board Certified Orthopedic Clinical Specialist in Physical Therapy, 24 years of experience)

I am cautiously optimistic in the intermediate term about the coming news. Short term, I would not be surprised if we see some down-time for Salvy. Let me explain.

This straight hyperextension injury can really cause one of two issues. First, hyperextension may result in a deep chondral bruise (a bone bruise). Only time will make this better. There is no shortcut. Second, the ONLY ligament vulnerable with hyperextension is the ACL.

Of the two mechanisms of injury resulting in ACL tear, knee hyperextension is the less common. More commonly, athletes suffer a non-contact injury where the knee bends outward (knee valgus) in 20-30 degrees of flexion and tibial (large bone in the lower leg) external rotation.

While knee hyper-extension is absolutely capable of tearing the ACL, the video demonstrates a degree of hyperextension, that while "guestimatable", is meaningless in terms of an individual. IF Salvy naturally has 10 degrees of knee hyperextension (I have 15 or so) AND he was able to fire his hamstring muscles in time (a reflexive contraction) he might be okay. If he has zero hyperextension, the ACL is at least stretched.

Bottom line:

First, there is cause for concern because he has an injury. Athletes don’t avoid loading the knee while walking for funzies.

Second, the CLINICAL (on the field/clubhouse) diagnosis of complete ACL rupture is pretty straightforward. The Lachman test has a very high degree of statistical specificity (the ability to rule in a disorder when compared to the gold standard MRI).

Here is where I am hanging my hat on: If Salvy truly told the club that he doesn’t have a serious injury, he probably doesn’t. For him to say otherwise would be irresponsible. I’m betting the athletic trainer told him the ACL is intact. That would be a huge sigh of relief.

This would also explain why they are doing an X-ray (if the reports are true). An X-ray cannot detect an ACL tear, but it may pick up a fracture. If he continues to have trouble bearing weight, an MRI is coming. If the trainer thought he blew his ACL, they would have gone straight for an MRI.

This is all speculation based on what the reports say so far. Let’s all hold our breath, cross our fingers and toes and hope for the best!


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