Injury Risk Assessment: Stop Injury Before It Happens

For most athletes, besides those that go pro, the highlight of their career is playing that big game senior year of high school.  The story reads something like this.

You are in the best shape of your life, you love the sport you’re playing, and your game is firing on all cylinders.  You have practiced like crazy to perform your best and make a difference for your team.  As the game starts, you focus in on the field and nothing else around you matters.  You are lost in the passion of pushing yourself to the limit.  Finally, it is your chance to shine as you receive a pass from your teammate.  Now that you are in control of the game you kick it into high gear and notice a defender coming at you full tilt.  In a flash, your nervous system, after years of training, responds to the defender and decides to hard cut right.  You plant your left foot and dig hard into the turf.  At that instant you hear a “pop” in your knee and intense pain is shot deep inside your leg.  You fall to the ground and grab your knee and something inside you just knows your senior sports year is over.  As you limp off the field with the help of a teammate you ask yourself, “how did this happen--am I going to be able to play again?"

http://deansomerset.com/acl-injuries-and-downhill-skiing-how-to-prevent-them-and-still-be-a-bad-ass/ Does this story sound familiar?  It is a memory I will never forget. 

I tore my ACL, meniscus, and MCL playing football my junior year of high school.  It was a devastating injury that sidelined me for 1 full year from competitive sports.  During that time, I learned a great deal about injury, rehabilitation, fitness, health, and I also learned a great deal about the mental struggle that comes with injury.  Serendipitously, my injury ignited a passion for health, rehabilitation, and injury prevention previously dormant inside of me.  My experience recovering from ACL surgery launched my career in physical therapy and brought me to where I am today with my specialized sports and physical therapy clinic Competitive EDGE Physical Therapy in San Jose California.  I am devoted to preventing injury in high school, college, and professional athletes.  This post will discuss ACL injury risk assessment and its tremendous value for athletes, coaches, and sports teams.

How Common are ACL Injuries?

It is likely that you know of someone who has undergone ACL surgery.  ACL injury is most likely to occur in basketball, soccer, skiing, football, and lacrosse since sharp cutting and twisting are inherent to playing these sports.  ACL injury is most common between the ages of 15-35 due to the high level of activity associated with this age group.  Research demonstrates that males have a higher reported amount of actual ACL tears.  Females; however, are 2-8 times more likely to sustain an ACL tear versus males at the collegiate level.  Approximately 200,000 ACL injuries occur per year with 50% of those requiring reconstruction surgery.   The fact that always blows me away is that 70% of all ACL tears happen due to non-contact mechanisms.  That means that 70% of ACL injuries occur without anyone touching the athlete.  Likely, these athletes demonstrated altered biomechanics with running, cutting, jumping, and stopping placing higher strain on the lower extremity and ACL.  It is in this population that injury prevention screening and training would be greatly beneficial.  

What are the Risk Factors Associated with ACL Tears?

There are many risk factors associated with non-contact ACL tears.

  1. Poor Lower Extremity Alignment
    1. Pelvic drop with single leg activities
    2. Knee genu valgus (“hip adduction” where knee moves inward)
    3. Femoral internal rotation (the thigh bone rotates in towards the groin)
  2. Poor trunk control (lateral trunk lean, twisting of the trunk)
  3. Foot pronation
  4. Female athletic triad (amenorrhea, eating disorders, osteoporosis/osteopenia)
  5. Gluteus maximus/medius weakness
  6. Quadriceps weakness
  7. Decreased knee flexion angle with loading
  8. Upright trunk posture with loading
  9. Higher ground reaction forces
  10. Congenital anatomical factors (wider pelvis, femoral anteversion)

Increased hip adduction angle with drop jump

Ground reaction force vector lateral to knee showing knee valgus and lateral trunk lean


How are These Risk Factors Observed?

The best way to observe biomechanical risk factors for injury are at game speed in sport based movements.  Some of these movements can be tested with a slow speed squat or step down; however, this does not match the forces required during athletic competition.  In order to observe these motions in their native environment you need high speed video. Typically, the video must capture the motion at least at 100 frames per second to limit blurring and inaccuracy of measurement.   Additionally, the video should capture both the view from the front of the athlete and the side view.  It is then possible to observe trunk control, pelvic control, and lower extremity alignment.  

Along with high speed video, motion capture tools with LED lights or movement sensors provide higher accuracy of measurement.  By recording real-time joint angles, you can further demonstrate side to side differences in shock absorption, alignment, and motor control.  Joint angles also offer concrete data to test and re-test to determine progress and to compare to a set baseline.  Additional equipment like a force plate can track actual forces exerted on the environment further tracking loading, shock control, and power development. There are also specific quick tests that can be performed that will provide an athlete’s injury risk compared to their peers of similar age, sport, and competition level.  These include the Y balance test, functional movement screen, and single leg hop for distance.  These, as well as the previous testing outlined, should be provided by a physical therapist or professional with specialized sport and orthopedic certifications.

How are These Risk Factors Changed?

Biofeedback tools such as high speed video, joint angle tracking, force plate measurements, and muscle electromyography will provide concrete measurable data.  The most important tool at the athlete’s disposal is video.  Seeing exactly how you move makes practicing correct movement easier to grasp and compare to a norm.  Learning proper motor control takes practice and many repetitions to make permanent.  Correctly timed feedback coupled with progressive and more challenging practice is the best way to improve motion.  The ultimate goal is to perform the movement skill for your sport perfectly at game speed.  This should be part of your discharge testing for return to sport. In order to change sport based movement an athlete needs to be strong enough to perform the new movement pattern.  A proper strengthening program needs to be initiated with the focus on using the right muscles to perform the action.  Often athletes are excellent at compensating for weakness and someone may look quite strong but in fact lack the necessary strength in the tissues needed to avoid or recover from injury.  For instance, many male and female athletes have very strong quadriceps, but they lack strength at the gluteus medius and maximus muscles leaving them with lower extremity alignment issues such as genu valgus, pelvic drop, or femoral internal rotation.  Muscular strength adaptations take time, weeks to months, and an athlete should spend the necessary time to develop this strength.  Without a proper base of strength, then motor control, power, and agility training would just increasethe improper movement pattern.

Strength, Range of Motion, and Lachman's Testing are NOT Enough

Typically, return to sport testing is diminished to range of motion, strength, and Lachman’s testing.  To be cleared for sport an athlete must have full painlessrange of motion.  That means the knee needs to straighten fully and bend fully, equal to the other leg, without pain.  An athlete also needs to have full gluteal, quadriceps, hamstring, calf, and core strength.  This is typically measured by pushing into the hand of a physical therapist or doctor.  A Lachman’s test is a test used to determine the integrity of the ACL.  The idea is to translate the tibia forward on a fixed femur and feel if there is any laxity in the joint.  To pass this test the ACL needs to be very stable without laxity.

Although these tests are essential, they are for the most part static.  By static I imply that the patient is either sitting or lying down for the testing.  This will tell us the anatomical and physiological condition of the ACL and lower extremity but it fails to tell us how those tissues function for sport.  Sports are dynamic and therefore dynamic testing is necessary.  If avoiding injury was just about being flexible and strong then gymnasts would have a very low rate of injury considering they are both strong and flexible.  If any of you have been or know a gymnast you understand that injury is the norm in that sport not the isolate incident.  It is therefore to provide dynamic testing to determine sport readiness. 

The Future of ACL Injury Prevention

Current research shows that we need to do a better job of preventing ACL injury and do a better job of returning athletes to injury free sport participation after ACL reconstruction.  It has been estimated that athletes who undergo ACL injury and return to sport are up to 15 times more likely than their counterparts to sustain an additional injury of any kind.  In the NFL the overall rate of full return to sport is only at 63%.  That means that approximately 1/3 of professional footballers who sustain and ACL injury never return to playing football.  Athletes 18 years old or younger who have undergo ACL surgery have an 18% risk of tearing the ACL on the opposite leg.  If you are over 18 years old the overall ACL injury rate is between 4-7%.  

These are surprisingly high numbers for re-injury following surgery.  This data speaks to the fact that knee and lower extremity control is complex and an athlete needs consistent and focused training to learn proper motor control.  ACL prevention and rehabilitation needs to utilize current technology, research in neuromuscular control, and comprehensive plans of care to improve patient outcomes.  Medical professionals also need to be honest with athletes about the duration of rehabilitation for a safe return to sport.  It may be possible for some highly skilled athletes to return to sport 6 months after ACL reconstruction but the more likely return to sport time is 1 year.  In fact, there is a higher rate of injury when returning to sport before the 1 year mark.  By being honest up front with athletes they can better mentally prepare for rehabilitation and not struggle emotional setbacks along the way.

Pre-game warm up programs such as FIFA 11 and PEP have been very successful at decreasing the rate of ACL injuries in sport.  These programs should be implemented in competitive sports starting at middle school.  It is incumbent on movement professionals such as physical therapist and athletic trainers to start these programs at local schools and teams.  Additionally, educational seminars on ACL injury risk factors should be presented to sports coaches, parents, and athletes to raise awareness.  These programs can open doors between coaches, strength and conditioning specialists, and physical therapists creating an optimal team for athletes.   I hope injury prevention is taken seriously as a proven way to help athletes stay healthy and play the games they love.  Please feel free to contact me at Competitive EDGE Physical Therapy about establishing an injury prevention program for your team, school, or athletic organization.  I have experienced sports as a patient and medical provider and I know there is work to be done! If you would like to speak with Kevin about injury prevention screens, evaluations, and team education please call 408-784-7167 or email kevin@compedgept.com

Written by :
Kevin Vandi DPT, OCS, CSCS
Physical Therapist in San Jose-Los Gatos-Campbell-Almaden