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Brian Schiff’s Blog

Injury Prevention, Sports Rehab & Performance Training Expert

Tag: ACL injuries

Poor landing mechanics are often cited as a predictor of ACL injury risk. In my 20 years as a physical therapist, I have rehabbed many athletes with this injury. I believe that injury prevention, whether to prevent a primary or secondary injury, hinges on the ability to train the body to decelerate and land appropriately. Some athletes simply move better than others. Nonetheless, teaching a soft bent knee landing while minimizing dynamic valgus is essential.

The following video from my online PFP column reveals a foundational exercise that can be used in prevention and rehab alike.

Click here if you want to read about another landing exercise that I utilize in my training and rehab programs.

I rehab far too many athletes under the age of 18 with ACL tears. In many cases, I am rehabbing some who have suffered multiple ACL ruptures before they graduate from high school. The burning question is why do so many clients suffer a graft failure or contralateral injury so so often?

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Is it related to genetics? Is sports specialization to blame? Perhaps fatigue and limited recovery is a problem. I think the answer is multifactorial, but to be perfectly honest we as a profession have yet to truly arrive at a consensus as to when the “right time” to return to play is. Opinions vary widely based on the athlete, sport, native movement patterns, graft choice, additional injuries (ligament, cartilage or soft tissue) and the provider.

As a clinician dedicated to both prevention and the best rehab, I am always re-evlauating my own algorithm and rehab techniques, while looking for scientific rationale to direct my exercise selection and decision making processes. A recent paper by Webster and Feller in the November 2016 edition of AJSM looked at subsequent ACL injuries in subjects who underwent their primary ACLR under the age of 20 utilizing a hamstring autograft reconstruction procedure.


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Perhaps one of the most researched topics is ACL injuries.  I have been studying and working for years in my clinical practice to find the best ways to rehab athletes following injury as well as implement the most effective injury prevention strategies.  Prior studies indicate prevention programs even when self directed can be successful.

However, on the whole injury rates have not declined over the past decade or so.  Much attention has been given to valgus landing mechanics, poor muscle firing, stiff landings, genetic difference between males and females, ligament dominance, quad dominance, and so forth.  The predominant thoughts today for prevention center around neuromuscular training and eliminating faulty movement patterns (refer to work being done by Timothy Hewett and Darin Padua).

We also know from a biomechanical standpoint that the hamstrings play an integral role in preventing excess anterior tibial translation, and as such hamstring strengthening needs to be a big part of the rehab and prevention program.  I believe in hamstring training that allows for activation in non-weaightbearing and weight bearing positions.  Common exercises I will use include:

  • HS bridging patterns (double /single leg, marching, knee extension, stability ball)
  • Nordic HS curls
  • HS curls (stability ball, TRX or machine)
  • Sliders - focus on slow eccentric motion moving into knee extension followed by simultaneous curls/bridge
  • Single leg RDL (add dumbbells or kettle bells for more load)

Note: click on any of the thumbnail images above for a full view of the exercise.  From left to right: Nordic HS curls, sliding hamstring curls and single leg RDL).

A recent blog post entry by the UNC Department of Exercise and Sport Science (@UNCEXSS) has spurred my post today.  Click here to read their entry on optimizing injury prevention based on work done by Professor Troy Blackburn regarding the effect of isometric and isotonic training on hamstring stiffness and ACL loading mechanisms.  The research that was done holds promise for hamstring training designed to increased musculotendinous stiffness (MTS).


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I had the pleasure of listening to Darin Padua, PhD, of UNC present some of his latest research on ACL injury prevention last week. He has been doing research for some time. One of his studies (JUMP ACL) in collaboration with the military and several others has looked at prospective data and injury occurrence among college age subjects.

Much of the research to date on injury prevention has been done by Timothy Hewett and his colleagues. It has concluded that drop landing with a valgus collapse (hip abduction/IR with valgus knee moment) is a risk factor for injury. Interstingly enough, despite that knowledge and the proliferation of prevention programs, Darin mentioned that overall these prevention programs have not slowed the rate of ACL tears in the last decade. Why is that?  He also relayed that much of what we know now is based on 15 total cases.

The Jump ACL Study in a nutshell lasted for 5 years at 3 different military academies:

N = 5,700 cadets with no prior ACL surgery

  • Soccer players = 1,690
  • Tested from 2005 to 2008
  • 39% female; 25% NCAA athletes
  • 14,653 person-years of follow-up

N = 113 incident ACL injuries

  • Soccer players = 29
  • Mean time from testing to injury = 3.1 yrs
  • N = 92 one ACL injury; N = 11 two ACL injuries

Some data (will be published) he discussed based on his findings revealed the following about high risk profiles for ACL injury:

  • Hip flexion > 40 degrees at landing = 1.76x increased risk
  • Hip adduction plus knee valgus = 3x increased risk
  • Hip adduction plus knee varus = 27x increased risk

He also mentioned that the high risk profile does not correspond to the ACL injury event profile of:

  • Hip abduction
  • Lateral trunk flexion
  • Knee valgus collapse
  • Small knee flexion
  • Tibial ER/IR

In the end, he suggests we need to better understand who to target (high risk profile clients) and what to modify (injury event profile) so we can better customize injury prevention programs that optimize proper movement and meet the needs of each individual athlete.  He reminded us that using the uninjured side for comparison is insufficient as faulty movement patterns already likely existed contributing to the first ACL injury.

So, assessing movement continuously and striving for excellent movement quality is a MUST if we are going to both prevent initial ACL injuries and reduce the re-tear rates for our athletes we send back to play.  He reports that those at increased risk simply have bad biomechanics.  His message provides more weight to having an advanced algorithm to identify asymmetry, poor motor control and flawed movement patterns in order to effectively prescribe interventions to address these things.

At UNC they use a PRIME assessment.  I am excited to learn more about it and have referred one of my female higher level soccer players to their lab for assessment as I look at this return to play decision with her now that she is just past 7 months post-op.   I think the hip/core obviously play an important role as I see so much deficiency in my female patients recovering from injury.

Clearly his findings with hip adduction and varus as a big risk factor seem to indicate it could be a top down kinetic chain breakdown as well upon impact based on the risk profile.  Pelvic stability or the lack thereof seems to be significant, only NOT in the same manner we thought about it before based on previous research available.  Stay tuned, as we have lots more to learn about ACL injuries and how best to tailor our prevention efforts.

ACL injuries continue to proliferate among female athletes.  I am passionate about preventing them, and part of my professional mission is to study and evolve in my rehab and prevention training approaches all the time to stay on top.  I wanted to pass along some new information on a new screening tool just unveiled in the Strength and Conditioning Journal this month.

Before I reveal the screening and training tool, I want to take a moment and review what Timothy Hewett refers to as modifiable risk factors that contribute to injury risk based on his work:

  1. Ligament Dominance - defined as an imbalance b/w neuromuscular and ligamentous control  of dynamic knee stability and it is visualized by loss of frontal plane control with landing and cutting
  2. Quadriceps Dominance - defined as an imbalance between quad and hamstring strength, recruitment and coordination
  3. Leg Dominance - defined as an imbalance between the two legs with respect to strength, coordination and control
  4. Trunk Dominance ‘Core’ Dysfunction - defined as an imbalance b/w the inertial demands on the trunk and its ability to resist or control/resist it

Previously, Hewett has identified that high knee abduction moments are related to high LOAD on the knee and a major risk factor for ACL injury.  He and his colleagues have done extensive motion analysis in their lab in Cincinnati, OH.  As such, a drop landing test has been used as one tool to observe landing mechanics and assign some risk value to athletes competing in cutting and jumping sports.

In the current article (click here for the abstract) Meyer, Brent, Ford and Hewett unveil a new screening tool involving the tuck jump.  They propose that this tool is easier for the S & C coaches to do on the field and not only assess risk factors by way of observing technical flaws, but also use the tool as a training maneuver.

The idea is the subject will perform tuck jumps for 10 seconds consecutively while the observer makes notes on the following pre, mid and post jumping:

  1. Lower extremity valgus at landing
  2. Thighs do not reach parallel (peak height of jump)
  3. Thighs not equal side-to-side (during flight)
  4. Foot placement not shoulder width apart
  5. Foot placement not parallel (front to back)
  6. Foot contact timing not equal
  7. Excessive landing contact noise
  8. Pause b/w jumps
  9. Technique declines prior to 10 seconds
  10. Does not land in same footprint (excessive in flight motion)

Factors 1-3 refer to knee and thigh motion, 4-7 refer to foot position during landing and 8-10 refer to plyometric technique.  Coaches are instructed to grade the flaws if seen with check marks during the phases they are seen and use this as a guide for correction.  They may also use cameras in the frontal and sagittal plane to assist them.

My thoughts on this are:

  • There is sound science behind the rationale for the test and modifiable risk factors
  • There is a need for basic no-cost screening tools coaches can apply in their settings
  • The tuck jump assessment will provide instant feedback on form and identify technical flaws that may indicate higher risk for injury
  • The tuck jump is a higher demand plyo drill so I fear poor form may be as much to blame on inexperience and unrefined motor patterns as it is to just dominance patterns so we need to keep plyo training experience in mind when analyzing the screen results especially for beginners
  • The tuck jump assessment does not really consider fundamental movement restrictions that may bias the form on one side if an asymmetry is present
  • I still wonder how much ankle pronation impacts landing and whether we will see more research on this - there was a study done at ECU where they used orthotics and saw a reduction in ACL tears in their collegiate athletes so I have to wonder about this crucial element of the kinetic chain

In the end, we still lack many answers.  According to data published in the Journal of Athletic Training in 2006, non targeted neuromuscular training programs need to be applied to 89 female athletes to prevent 1 ACL tear.  So, we need to keep studying and applying science to our training, all the while critically questioning science and looking at our athletes holistically to find the best prevention strategies for each one individually and for at risk athletes as a whole.