Monday, May 21, 2018

Assessing Risk - Is It Possible: Part II

From our last series, we know that previous knee injury does impact future performance.  During that discussion, we highlighted a study by Johnston et al that looked at the position of the lower kinetic chain at the time of injury.  This study was done via video analysis of footage of NFL game and practices during the time of the athlete's ACL injury.  We know from this study that non-contact ACL injuries occur when the limb is place in a position of dynamic valgus and under high loads (shifting position).

Last week we began the discussion to see if this is the position just for professional players or do younger athletes also present with a similar position during non-contact ACL injuries.  For this discussion we looked at recent study by Owusu-Akyaw et al which analyzed bone bruise patterns in younger athletes.  Based on these results, the dynamic valgus position (flexion, valgus and internal rotation) is a position that results in ACL rupture in male and female athletes under high loads.  Based on the results of both of these studies, then it would make sense that we must find ways to assess this in our athletes.  To do so, we should look at the literature and see what is currently being used to assess athletes for risk.

One test that is being used to assess athletes for risk is the single leg hop test for distance.  During this test, the athlete stands on the leg to be tested.  They will then hop as far as possible and land on the same limb.  This is repeated on the contralateral limb.  This is typically performed three times and the distance is measured for each.  Using the average of the three, the assessor is looking for limb symmetry (being equal on both sides) within 85%-90%.  The assumption is that if limb symmetry is achieved that the athlete is not at risk.  This is a common tool that is being used to assess risk in pre-participation physicals and for return to play following ACLR.


In 2015, Rohman et al published a paper in the Am J Sport Med looking at limb symmetry in athletics.  What they found was that 93% of norms had limb symmetry greater than or equal to 85%.  So if norms have 85% limb symmetry, what should be the number for those at risk.  Most physicians will use 85%-90% of the contralateral limb.  Considering this study however makes us question if an athlete is at 85% are they really at risk?  I am not sure if we know the answer to this question but it is something we need to consider when making these kinds of calls with the above mentioned test.  

For demonstration purposes, let's suppose the athlete has 95% limb symmetry on the single leg hop for distance test.  Is this athlete at risk or are they ready to return to play.  If we only consider the above information, we might say yes.  According to the Johnston et al study and the Owusu-Akyaw et al previously mentioned, we need to measure dynamic valgus to assess risk as these are the movements that rupture the ACL under athletic types conditions.  If an athlete is demonstrating 95% limb symmetry on this test, is this indicative that these movement patterns are not occurring?

Or, could an athlete perform this test and be 95% symmetrical and still demonstrate the movement patterns shown here.  The assumption is that with all of the hop tests (single leg hop for distance, triple hop for distance and lateral hop) that symmetry = good biomechanics.  But is this the case?  What we see anecdotally is this is not the case.

This is what we see but what does the literature tell us.  Next week we will look into this.  Make sure to stay tuned.  Please make sure to check out our new website at www.iceperform.com where our goal is to help you help others.  #ViPerformAMI


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.  He is the founder | developer of the ViPerform AMI, 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 is also a competitive athlete in Brazilian Jiu Jitsu. 

Monday, May 14, 2018

Assessing Risk - Is It Possible?

Over the course of the last blog series, we discussed whether previous knee injury impacts future athletic performance.  There was compelling evidence presented throughout this series that previous injury not only has an impact on future performance but also health care costs.  The Mia et al study in 2017 made it pretty clear, that at least in NFL football players, there was a big impact on performance up to 2 years post ACLR and professional players' careers were decreased by 2 years. 

In this series, we also discussed in this study what is the most common mechanism for an ACL injury in football.  In the Johnston et al study in 2018, the authors found that a majority of ACL injuries in the NFL are non-contact in orientation and that the limb is in a position of dynamic valgus (as seen here).  These results led the authors to suggest that there should be some targeted programs designed to assess and control valgus. 

Although it is great to work with professional athletes, the majority of us don't get that opportunity and therefore the majority of our population is youth athletics.  Frankly, these are the ones that should have our major attention, especially when it comes to injury prevention.  This last weekend at the Andrews Institute's Annual Injuries in Football Course, Dr. John Polousky presented on the youth ACL epidemic.  He stated there are some 45 million kids that participate in organized athletics and roughly 50% of all sports related injuries are due to overuse.  Current literature shows that 1 in 4 elementary and middle school aged kids suffer an ACL injury at some point in their athletic career accounting for ~200,000 ACL injuries in youth athletics.

As a parent and health care provider, this is unacceptable!  We have to do something about it and if we don't we are adding to the problem through our own negligence.  According to the Johnston study cited above, we know movements that put the athlete at risk for non-contact ACL injuries, at least in professional players.  But does that apply to youth athletics? 

That will be the first thing we will look at in this series.  We will start off this discussion by looking at a recent study by Owusu-Akyaw et al in the American Journal of Sports Medicine 2018. 

Determination of the Position of the Knee at the Time of an Anterior Cruciate Ligament Rupture for Male Versus Female Patients by an Analysis of Bone Bruises

Background: Female athletes rupture their ACL at a rate 2 to 4 times higher than their male counterparts.  As such, several studies have looked if males and females sustain ACL injuries vai different mechanisms.  By understanding the mechanism, we can then create assessment tools and injury prevention programs to address. 

Hypothesis: Compare the knee position at the time of the non-contact ACL injury between the sexes.  It is the hypothesis of the authors that there will be no differences in the position during injury. 

Methods: T2 MRI scans were retrospectively reviewed for 30 athletes (15 male and 15 female) who sustained non-contact ACL ruptures.  MRIs were performed within one month of the initial injury.  All participants had contusions associated with the ACL injury on both the medial and lateral articular surfaces of the femur and tibia.  3D models of the femur, tibia and bone bruises were created via segmentation on MRI (pictured to the right).  The femur was positioned relative to the tibia to maximize bone bruise overlap, thereby predicting the bone positions near the time of injury.  Flexion, valgus, internal tibial rotation and anterior tibial translation were measured in the predicted position of injury.

Results | Conclusion: There is no statically significant difference between male and female knee positions during the time of ACL injury.  The results suggest a similar mechanism of injury for both the male and female athlete. 

Obviously this is a very novel approach to determining knee position during a non-contact ACL injury.  In most settings, video review would be the gold standard as you get to see actual footage of the limb position at the time of the injury.  In professional sports this is great and with the amount of videoing that is occurring in practice and game time, you can be pretty much assured this will be captured.  However, in youth athletics, it is rare that video footage exist where the the mechanism of injury is captured.  As such, this novel approach could provide some great insight as to the limb position during injury. 

Although this is based on solid biomechanics, it still is not the gold standard.  As such, there are some other factors that may impact this.  For example, we are basing this off the assumption that the bone bruise occurred at the time of the injury.  But, what if the bone bruise did not occur at the time of the injury.  What if the athlete continued to play and that resulted in the subsequent bone bruise?  This would then provide a false reading and led to a misinterpretation of the limb position at the time of the injury. 

This has to be considered but in reality it is most likely that the bone bruise did occur at the time of the initial injury.  The mechanism of injury (flexion, valgus and internal rotation), is very similar to what other studies have reported and what the previous Johnston study reported on video review of non-contact ACL injuries.  Based on the results of these studies, as well as numerous others, it is clear we need to assess the ability to control dynamic valgus at the knee.  Not only do we need to assess that but we need to:

  • Assess ability to control during single limb performance
  • Assess ability to control during multidirectional tasks
  • Assess ability to control both the motion and speed at which that motion occurs
Next week, we will look at some current methods we are using to assess this for determining return to play of athletes and see if this has the ability for use in determining risk in pre-seasons physicals.  Please make sure to check out our new website at www.iceperform.com where our goal is to help you help others.  #ViPerformAMI



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.  He is the founder | developer of the ViPerform AMI, 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 is also a competitive athlete in Brazilian Jiu Jitsu. 


Monday, May 7, 2018

Does Previous Knee Injury Impact Performance & What Can We Do About It? - Part V


Over the course of the last several weeks, we have been looking at the impact that previous knee injury has on future performance.  Knowing that previous knee injury does impact performance this led us along the logical progression of how do we assess this risk factor and more importantly is there anything we can do about it.  The Johnson et al study guided us on what we should be assessing and the Lopes et al study let us know that we can change these biomechanical factors with the right program. 

Knowing that we can impact injury rates with the right program and that we are assessing athletes for ability to stabilize their lower kinetic chain in frontal plane, it would make sense that programs that focus and train these principles would be more effective.  That led us to the Omi et al Am J Sport Med2018 study.



Effect of Hip-Focused Injury Prevention Training for Anterior Cruciate Ligament Injury Reduction in Female Basketball Players: A 12-Year Prospective Intervention Study.

Purpose: The purpose of this study was to determine the effectiveness of hip focused ACL injury prevention program in female basketball players.

Methods:  This was a prospective intervention study conducted for 12 years.  During the 4 year observation period, incident rates of ACL injuries were collected from female college basketball players.  Following the observation period, a hip focused ACL injury prevention program was implemented for 8 years (the intervention period).  A total of 309 players (age 19.6 years ± 1.2 years, height 163.7 cm ± 5.6 cm, weight 59.1 kg ± 5.1 kg) were tracked and compared with 448 players (age 19.6 years ± 1.1 years, height 162.6 cm ± 5.8 cm, weight 58.0 kg ± 5.7 kg) who participated in the intervention period.  Athletic exposures, ACL numbers and mechanisms of injury, relative risk and absolute risk reduction, numbers need to treat and compliance were analyzed.
Results:

ACL Injuries during the 4 year observation period
  • 16 ACL injuries
  • 13 of which were non-contact in orientation (81.3%)
  • Avg. 4 ACLs/year
  • Incident rate = .25/1000 AEs



ACL injuries during the 8 year intervention period
  • 9 ACL Injuries
  • 8 of which were non-contact in orientation (88.9%)
  • Avg. 1.1 ACL/year
  • Incident rate = .10/1000 AEs



Discussion:  The hip focused injury prevention program demonstrated significant reduction in the incidence of ACL injury in female collegiate basketball players.  This particular program has a significant focus on hip strengthening and single limb performance.  In addition, there is a fair amount of focus placed on technique and control of the knee in the frontal plane. 

Considering the Lopes et al study and the Omi et al study, one might conclude that assessing an athlete prior to performance of a program like this would not only allow us to measure the pre/post impact to the intervention but also may assist us in progressing an athlete through the series of the exercises to a higher level once stability in the frontal plane is obtained. 

So now that we know what to do about it, we now have some ways we can assess and based on that assessment drive a corrective program.  The final question we need to look at is what we do with those athletes who have had an injury.  Is there anything we can do to help them return to play without increasing risk for reinjure and reducing the impact there is on performance?  To close out this series next week, we will look at the Wren et al study looking at hop test and whether or not this this a good test for return to play.  Next week we will look at the Wren et al J Orth Sport Phy Ther 2018 study.


Also, please make sure to check out our new website at www.iceperform.com where our goal is to help you help others.  #ViPerformAMI


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.  He is the founder | developer of the ViPerform AMI, 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 is also a competitive athlete in Brazilian Jiu Jitsu. 






Monday, April 30, 2018

Does Previous Knee Injury Impact Performance & What Can We Do About It? - Part IV


Throughout the course of this blog series we have been discussing if a previous knee injury impacts   We believe the answer to this question is pretty clear that yes, previous knee injury does impact current and future performance.  We know this to be the case in Division I athletics (Rugg et al Am J Sports Med 2014) and in professional athletics (Mai et al Am J Sports Med 2017).  We also know that football players are impacted to a greater degree than basketball players and hockey players respectively.  We further discussed what the literature indicates what we should be assessing to prevent these injuries (Johnson et al Am J Sport Med 2018) and whether or not fatigue plays a role in injury.  

This is all great information to have but if we don’t know what to do with this information or more importantly how to impact it, what does it matter?  In this week’s blog, we will dive into that question.  What can we do about it? 
future athletic performance.

In this discussion, we will look at two different recent studies.  The first looking at whether or not injury prevention programs truly impact injury rates.  Lopes et al Am J Sport Med 2018 performed a systematic review with meta-analysis on whether injury prevention programs impact biomechanics of landing tasks. 

The Effects of Injury Prevention Programs on Biomechanics of Landing Tasks: A Systematic Review with Meta-analysis.  

Purpose: Synthesize the evidence on the effects of injury prevention programs on landing biomechanics as they relate to ligament, quadriceps, trunk and leg dominance theories associated with ACL risk.

Methods:  Six databases were searched for studies that investigated the effects of injury prevention programs on landing tasks biomechanics.  Prospective studies that reported landing biomechanics at baseline and post IPP were included. 

Results: 28 studies met the criteria which included a total of 466 participants.  Most studies
evaluated:
  • Young female athletes
  • Bilateral landing tasks
  • Recreational athletes
Factors that improved after implementation of injury prevention program include:
  • Peak knee abduction moment decreased
  • Hip flexion angles at initial contact increased
  • Peak hip flexion angles increased
  • Peak knee flexion increased
  • Peak knee flexion moment decreased

Conclusion/Discussion:  Based on the results of this systematic review, the exercises used in injury prevention programs might have the potential to improve landing biomechanics.  Peak knee abduction moment decreased which indicates that injury prevention programs influence a desired movement strategy.  This may help athletes overcome movements which result in excessive frontal plane motion of the knee resulting in dangerous ligament loads.  The results of this study lead the authors to further suggest that the results of these programs may be enhanced when they are developed based on the athlete’s baseline profile deficits. 

Based on this current systematic review as well as previous literature, we know that injury prevention programs can have a significant impact on biomechanical risk factors.  That said, it would seem logical that some may work better than others.  We know from the previous Johnson et al study discussed in the previous portion of this series that we should be assessing the ability to control dynamic valgus in single limb performance.  Based on this, it would make sense that programs that focus on controlling this frontal plane motion would be more effective.  So, next week we will dive into that by taking a look at the by Omi et al Am J Sports Med 2018.  Also, please make sure to check out our new website at www.iceperform.com where our goal is to help you help others.  #ViPerformAMI



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.  He is the founder | developer of the ViPerform AMI, 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 is also a competitive athlete in Brazilian Jiu Jitsu. 









Monday, April 23, 2018

Does Previous Knee Injury Impact Performance & What Can We Do About It? - Part III

In last week's discussion we discussed the Johnson et al study looking at the most common mechanism for injury in NFL players.  In this study, one of the results that came out was there was no association between injury mechanism and time of play.  This would indicate that fatigue does not play a role in athletes suffering a non-contact ACL injury or at least football players suffering a non-contact ACL injury.  This week, we are going to look into this discussion a little closer.

Currently this is a hot debate in the world of ACL injury prevention.  Studies are not clear one way or the other whether or not fatigue plays a role.  Santamaria et al in the Journal of Orthopedic and Sports Physical Therapy performed a systematic literature review which showed that the current body of literature was not clear on whether or not fatigue impacted biomechanics or injury rates.  One of the problems that the authors cited is there is no consistency in what researchers use for a fatigue protocol.  Some use the traditional treadmill test we use in VO2max testing, others use a percentage of max leg press while others use a timed run test.  The literature really is all over the place, so how do we truly know how mechanics are impacted if we are not even sure if we are bringing subjects into a truly fatigued state?

We know from Brazen et al work in the Clinical Journal of Sports Medicine 2010 that fatigue does impact movement during single leg landing.  In this study, the authors fatigued subjects and varified this using a percentage of maxEMG.  Once the subjects EMG level fell below a certain percentage the athlete was considered to be fatigued.  The athlete's biomechanics were measured pre/post fatigue in single leg drops.  What their results showed was that as an athlete's fatigue increased, there was an increase in frontal plane motion of the knee and higher peak vertical ground reaction forces.  Both of these factors are associated with increase in risk for lower kinetic chain injuries.

But this protocol is not being utilized across all studies and there is a plethora of other studies out there that are not showing fatigue plays a role.  So, one of the most logical things would be is to standardize the way we assess fatigue in studies.  The fatigue protocol we use in our setting is the FAST-FP (functional agility short term fatigue protocol).  Reason we use this particular protocol is the result of the Cortes et al study in the Journal of Sports Science in 2012.  In this study, the authors compared two protocols to see which had a larger impact on the lower kinetic chain biomechanics.  Specifically, which one resulted in altering mechanics as to indicate or reveal movement patterns which put our athletes at risk for injury.  This protocol is fairly simple and only takes 4 minutes.  During this, the athlete performs:


  • 20 second step up/step down to a 31 cm step at 220 btm
  • L drill with cones place 5 yards apart
  • Counter movement jumps - the athlete jumps 5 times up to a tape on the wall representing 80% max vertical height jump
  • Agility ladder - the athlete performs high knees up and down the 5 yard agility ladder.  First and third time is forward, second and forth time it is lateral.  
This whole process takes about 4 minutes.  The following video demonstrates an athlete going through one round of the FAST-FP.

So, we obviously need to standardize the way we implement a fatigue protocol in the research.  Maybe once we do this we can then see if there is an impact on injury rates following fatigue.  That aside, if you look at the literature on when an injury occurs during a game or competition, the literature  again is not clear on if this does in fact play a role.

Take the following "real life" case into consideration.  A 17 year old female soccer player playing high level club soccer.  She is competing in a tournament on Saturday and Sunday.  On Saturday she is a starter and plays in 3 games with the last game being a hard fought battle that concludes at 10 PM at night.  By the time she gets back to the hotel and in bed it is almost midnight and she is back on the field for the first game starting at 7 AM.  First play of the first game she tears her ACL.

Now, according to the literature, if we took her case and how this is currently analyzed, she tore her ACL in the first play of the game and therefore fatigue did not play a role.  However, any of us who have been athletes and who have dealt with a situation like this can attest, you are very fatigued at this point.  You have played hard for three games the day before, did not get much rest and are now playing higher level teams in the play off portion of the tournament.  But, according to the literature, this is not a fatigued player.

My point being, does fatigue not play a role OR have we simply not figured out a way to accurately assess that in the literature.  For me, I believe the later.  Sometimes we don't need a paper to tell you if you smash your finger with a hammer it is going to hurt.  It makes sense that fatigue would play a role.  I know when I am tired I move less efficiently and that my performance is impacted.  Although that is only an N of 1, it still follows general exercise physiology and biomechanical principles.

Next week, we will close out this discussion by talking about what do we do about this.  We know what the mechanism is, that it plays a role on future performance and that fatigue plays a role, but what do we do with all that information.  Stay tuned to find out next week.  Please make sure to check out our new website at www.iceperform.com.


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.  He is the founder | developer of the ViPerform AMI, 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 is also a competitive athlete in Brazilian Jiu Jitsu. 





Monday, April 16, 2018

Does Previous Knee Injury Impact Performance & What Can We Do About It? - Part II


Last week, we looked at whether or not an ACL injury impacts an athlete’s future performance.  Based on what we learned from the Read et al and Mai et al studies, we know that an ACL injury and ACLR does have an impact on future athletic performance.  So, the obvious take home is that we need to somehow try to prevent these injuries.  How do we do that?

If we take football in isolation, the obvious question becomes, how do NFL Players’ ACLs get injured?  Most would assume that in a violent collision sport like football that the injury occurs from a contact with another player.  Some in the media have suggested that as a result of the new concussion rules and players being required to hit lower, that this is resulting in an increase in ACL injuries.  This assumption is based on the assumed fact that the majority of ACL injuries in football are contact in nature. 

Based on an analysis of NFL data from 2013 to 2016, there were a total of 202 ACL injuries.  Of the 202 ACL injuries during this time, 73% (147) were non-contact in orientation.  This means that the mechanism of injury was not another player striking the knee or the player during the injury.   Further analysis reveals that 66% of ACL injuries in the NFL are isolated to 5 key positions:
  • Wide Receivers – 19.4%
  • Linebacker – 15.5%
  • Cornerback – 11.7%
  • Offensive Line – 10.7%
  • Defensive End – 8.7%
This data is based on public record and what information is available through the NFL.  But does this hold true in the research and if so, what is there a common mechanism that results in the player rupturing their ACL?

Johnson et al published a paper in the American Journal of Sports Medicine in 2018 that looked to determine just that. 

Purpose:  The purpose of this study was to describe the mechanism, playing situation, and lower extremity limb position associated with ACL injuries in NFL players through video analysis to test the hypothesis that a majority of injuries occur via a contact mechanism.

Methods:  In this study the authors performed a retrospective cohort of National Football League (NFL) players with ACL injuries from 3 consecutive seasons (2013-2016).  Of the 156 ACL injuries identified, 77 (49%) occurred during the regular season and playoffs with 79 (51%) occurring in pre-season and training camps.  Video analysis was available for 69 injuries which was reviewed to determine the mechanism of injury. 

Results: The majority of ACL injuries analyzed occured vai a noncontact mechanism (50 of the 69 or 72.5%).  The only exception to this was offensive lineman who had only 20% of their ACL injuries by noncontact mechanism.  The most common activity leading to the noncontact injury was pivoting or cutting.  The most common position of the limb during the injury was hip adduction/flexion, early knee flexion/abduction and foot abduction/external rotation.  There was no association between injury mechanism and time of play or playing surface.

Discussion:  The results of this study suggest that the majority of ACL injuries in the NFL occur from noncontact mechanism with the lower extremity exhibiting a dynamic valgus moment at the knee.  This lead the authors to suggest that to reduce these types of injuries prevention programs should assess for these movement patterns and develop intervention programs which address.

Aside from these points, there are also some additional key points that came out of this study. 

  1. Lineman are more susceptible to contact ACL injuries.  This fact has led a lot of teams at the professional and collegiate level to proactively brace players.  Conceptually this might seem like a great idea, but there is very little support that this prevents ACL injuries in contact sports.  Additionally, we need to think about what this brace does to gait (how you walk and run) and muscle EMG activity.  What we do know is that players wearing two ACL braces walks and runs with an altered gait and EMG activity of the quads and hamstrings is decreased.  So what is the answer?  We may not have the answer to that yet but we do need to think about how we address this.
  2. Over 1/2 of ACL injuries are in the preseason.  In preseason, a lot of players are coming into preseason and camp in a deconditioned state.  Knowing the majority of these injuries are non-contact in orientation, that certain biomechanics add to increased risk of these injuries and that targeted training programs have been shown to decrease risk for these injuries, it seems implementing a post season and preseason movement training program would be beneficial.  
  3. No association between injury rates and time of play.  This is basically stating that fatigue did not play a role in the non-contact ACL injuries.  There are several authors that suggest that fatigue does play a role and a whole other contingency that states fatigue does not play a role.  For those in the fatigue does not play a role camp, they site that the literature simply does not indicate this is the case. 
We are going to save this for our next discussion to look at, does fatigue play a role.  Stay tuned next week as we look at this in more depth.  Also, please make sure to check out our new website at www.iceperform.com where our goal is to help you help others.  #ViPerformAMI



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.  He is the founder | developer of the ViPerform AMI, 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 is also a competitive athlete in Brazilian Jiu Jitsu. 




Monday, April 9, 2018

Does Previous Knee Injury Impact Performance & What Can We Do About It?


One of the first questions an athlete, who tears their anterior cruciate ligament (ACL), will often ask their physician is if they will be able to return to play.  The answer most physicians provide is yes, 80-90% of athletes do return to play to the same level of play.  However, what coaches, strength coaches, athletic trainers and physicals therapists have often wondered is if that return to play really means the athlete is returning to their previous level of performance?  Over the course of the last decade, researchers have attempted to start answering this question. 

In 2014, Rugg et al published a study in the American Journal of Sports Medicine that looked at division I athletes who suffered an ACL injury prior to their division I career.  What this study showed was that athletes who had an ACL injury prior to their division I career were at an 8 fold increased risk of injuring their knee or ACL, would spend more time on the disabled list and would cost the university more money than a non-injured athlete.  These findings are nothing new to college athletic administrators and have often driven recruiting decisions.  Based on these findings, one may speculate that this is isolated to division I athletes.  Seeing the implications this could have in athletics, this has spawned more researchers to look into this subject more and try to provide more clarity. 

Does a previous ACL injury impact performance in the professional athlete?  This is exactly the question that authors are attempting to answer.  In 2017 Read et al published a study in the American Journal of Sports Medicine that looked at the impact of ACL injuries on defensive lineman’s performance.  What the authors of this study showed was that 61% of defensive lineman were able to return to play following an ACL reconstruction (ACLR).  This is a much lower number than what has been reported previously in both the literature as well as the orthopedic community.  This study further showed that NFL players who had an ACLR started in 24% less games (57% vs. 81%) and had 30% less solo tackles (2.38 vs. 3.44).  These results mean that the player is not only contributing less to the overall team’s performance as a result of the injury but the player’s personal income is also impacted.  Knowing that players at this level get bonuses based on performance, if their performance goes down then so does their personal compensation. 

So, is this just isolation?  Is there truly an impact to a player’s performance after an ACLR?  That leads to one of the current studies we would like to examine.  Mai et al published a paper in the American Journal Sports Medicine 2017 titled: Performance-Based Outcomes After Anterior Cruciate Ligament Reconstruction in Professional Athletes Differ Between Sport. 

Purpose: In this study the authors wanted to see if there are differences in performance-based outcomes that exist after ACLR between professional athletes of different sports.

Methods: In this study the authors looked at players from the National Football League (NFL), National Basketball Association (NBA), National Hockey League (NHL), and Major League Baseball (MLB) who had undergone a primary ACLR for an acute rupture.  Players were identified through an established protocol of injury reports and public archives. Sport-specific performance statistics were collected before and after surgery for each athlete. Return to play (RTP) was defined as a successful return to the active roster for at least 1 regular-season game after ACLR.

Results: Of 344 professional athletes who met the inclusion criteria, a total of 298 (86.6%) returned to play. Some interesting findings by sport:

  • NHL players had a significantly higher rate of RTP (95.8% vs 83.4%) and a significantly shorter recovery time than athletes in all the other sports.
  • NFL athletes experienced significantly shorter careers postoperatively than players in all the other sports and had the lowest rate of active players 2 and 3 seasons postoperatively.  NFL players also had a decrease in performance for up to 2 years postoperatively.
  • NBA players showed decreased performance at season 1 after ACLR but recovered to baseline performance during the 2nd season.

Discussion:  These findings provide some interesting points.  We know from the research and injury data that NHL players suffer less ACL injuries than NBA and NFL players.  There are several potential reasons for this including:

  • Biomechanics of movement – for the NHL player, their lower kinetic chain does not go through the similar biomechanical patterns as a running athlete.  Due to the skate and the skating motion, the forward propulsion is not the result of the bounding motion that a running athlete goes through. Therefore the ground reaction force and the adduction moments that other athletes are subjected to, the NHL player is not subjected to. 
  • Muscle physiology of movement – in NHL players, the forward propulsion that occurs requires a significant activation of the gluteus medius and gluteus maximus.  Both of these muscles are directly responsible for preventing of the adduction and internal rotation moments that occur at the knee and therefore are often not an area of great weakness in these athletes.

In addition to these findings in NHL players, some of the other results that stick out is the impact that an ACLR has to the NFL player.  Based on the results of this study, an NFL player who has an ACLR:

  • Will have their athletic performance impacted for up to 2 years after their ACLR
  • Will have their athletic career reduced by 2 years

These results can be devastating to an NFL player.  Considering that the average NFL player’s career is only 5 years, this can have a huge impact on their career earning potential.  In addition, if their bonuses from game to game and season to season depends on their performance, if their performance is decreased for 2 years post ACLR, then this also has a huge impact on their long term professional sports earnings. 

So, now that we know that most athletes’ performance is impacted by an ACL injury, how do we prevent them?  Stay tuned next week as we explore this question and more.


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.  He is the founder | developer of the ViPerform AMI, 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 is also a competitive athlete in Brazilian Jiu Jitsu.