The Evolving Knowledge of Movement - Part VI - What We Know Now

Over the course of the last year, we have talked a lot about dynamic valgus and how measurement of this during single limb performance is one of the key indicators of risk for lower extremity injuries in sports.  Last week, we discussed how the direction of movement can impact the speed which is also associated with risk.

Back in March, we did a series of blogs on the most current literature related to concussion and the impact that this has on lower kinetic chain injuries.  Gilbert et al Sport Health 2016 was one of the first larger studies that showed the correlation to concussion and knee injuries and then a systematic review by McPherson et al Am J Sports Med 2019 showed a strong correlation to concussion and non-contact lower extremity injuries.  I get that concussion impacts balance but why is it that those who are concussed have more lower kinetic chain and knee injuries?  If we could answer this question, could this be something we address as a part of our concussion protocol and help reduce?

So, the first question is why?  Why is it that those who have had a concussion are at higher risk?  Having measured lower kinetic chain biomechanics on 14K plus athletes and tracking history of concussion, we have seen some interesting trends which could assist us in getting these answers.  From the data that we have, some common trends we see and potential treatment impacts include:

• Frontal plane motion at the knee.  Those with a history of concussion tend to have more frontal plane motion at the knee in single limb performance.  We not only see that the magnitude of motion is greater but we also tend to see speeds of valgus that are higher.
• Frontal and Transverse motion at the hip.  Those with a history of concussion tend to have more difficulty stabilizing their pelvis in the frontal and transverse plane during single limb activity.  This results in a much greater center of mass displacement during single leg activities and could be one reason we see the next item impacted.
• Time to Stability.  During single leg hops and single leg hop plant, when the individual lands they will sometimes have additional smaller hops before they get stable and stop moving.  The time stamp from the point that they first land to the point at which they stop bouncing around is called time to stability.  What we know from Pappas et al Clin J Sport Med 2011 and others, is that the greater the time to stability the greater the athlete is at for a ankle injury.  Those with a history of concussion tend to have greater time to stability than a non-concussed athlete.  This may be the result of the inability to stabilize the pelvis in the frontal and transverse planes. 
• Loss of Balance - Athletes with previous history of concussion tend to have more losses of balance noted during single limb training.  This may again be the result of the lack of stability at the pelvis causing the COM (trunk) to move more during single limb activities.  
• Larger displacement on scatter plot.  If you were to plot a point on the floor where the athlete lands after single leg hop, you would start to see that most athletes' points would be
  
  closely grouped together.  This is called a scatter plot.  One thing we know is that athletes who's scatter plots are grouped closer together, those athletes suffer less ankle and LKC injuries.  However, athletes who have a much wider grouping of their scatter plot tend to loose balance more and tend to be at greater risk for lower kinetic chain injuries.  

Conceptually when we think about all of the above it makes a lot of sense.  Additionally, this also gives us things that we can measure with our concussed athletes that would help to identify those that are at greater risk for lower kinetic chain musculoskeletal injuries.  All of these are not things that are traditionally assessed with concussed athletes and may help us not only objectively quantify these measures but also help guide us on some interventions. 

Next week, we will begin to discuss how this may guide some of our intervention and specific exercises.  Stay tuned as I am super excited to share with you.  If you enjoy this blog, please share with your colleagues, athletes and training partners and please be sure to follow us on instagrm @ bjjpt_acl_guy and twitter @acl_prevention.  Train hard and stay well.  #ViPerformAMI #ACLPlayItSafe

Dr. Nessler is a practicing physical therapist with over 20 years sports medicine clinical experience and a nationally recognized expert in the area of athletic movement assessment and ACL injury prevention.  He is the founder | developer of the ViPerform AMI,  ViPerform AMI RTPlay, the ACL Play It Safe Program, Run Safe Program and author of a college textbook on this subject.  Trent has performed >5000 athletic movement assessments in the US and abroad.  He serves as the National Director of Sports Medicine Innovation for Select Medical, is Vice Chairman of Medical Services for USA Obstacle Racing and movement consultant for numerous colleges and professional teams.  Trent also a Brazilian Jiu Jitsu purple belt and complete BJJ/MMA junkie.