Monday, July 3, 2017

Is There A Secret Sauce? - Part V Cont

Gradients of Gluteus Medius Weakness – Part II
Last week we discuss the function of the gluteus medius in both an open kinetic chain and closed kinetic chain.  Now that we know the function of muscle, what kind of movements will we see?  The most obvious is adduction in the frontal plane (like pictured in the above athlete).  When we see movement like that and we have identified it is coming from the hip and not the foot, we know that the gluteus medius is playing some role in that.  But what about the cases where the lower limb (femur) is stable?  We know that the gluteus medius also has an impact on stability at the pelvis, so what kind of movement would we see at the pelvis and if we see movement at the pelvis, does varying movements indicate a gradient of strength of the gluteus medius? 
According to Palastanga et al, we know that the gluteus medius “controls” pelvic rotation when the lower limb is stabilized.  It is well accepted in the literature as well as the medical field that weakness of the gluteus medius can result in a trendelenburg at the hip during gait (walking).  In the example pictured here, the right hip drops during stance phase on the left leg.  The arrow indicates that it is weakness of the gluteus medius on the left side that allows the pelvis to drop on the right.  With the origin and insertion of this muscle on the iliac crest and femur, shortening (or contraction) of this muscle would result in pulling the left pelvis down which would raise the right hip.  This is seen a lot in patients who have suffered a neurological insult (stroke) and who have a gluteus medius weakness as a result.  However, you can also see this in athletes.  In athletes, you will not typically see this in walking gait, but you will start to see this in running gait and in jumping.  Because of the ballistic nature of these movements, this occurs as a result of much higher ground reaction forces that occur with sports and are often much harder to see.  If you look at the high school football player pictured here, you can clearly see a trendelenburg that is occurring with a single leg hopping activity.  This trendelenburg is not apparent in his normal gait cycle.  However studies show that jumping results in ground reaction forces that are 4-8 times body weight whereas walking is traditionally 1 to 1.5 times body weight.  Hence, when we have an athlete do more difficult movements (single leg squat or single leg hop), then this lack of control at the pelvis then becomes more apparent. 
But, we also know that with greater weakness comes more significant deviation.  In the knee, this is represented as a larger increase in the frontal plane adduction and hence an increased adduction moment.  But, if the lower limb is stable, how does that appear at the pelvis?  Again, looking at some of the stroke literature, we know that patients who tend to have decreased MVC of the quadriceps that they hyperextend their knee.  Why do they hyperextend their knee?  Subconsciously, they have figured out that they cannot sustain a flexed knee posture so they hyperextend their knee to create more bony stability (created by bony stability with increased contact with femoral condyles and the tibial plateau).  This position, although it provides stability, also results in a decrease in MVC of the quadriceps.  Something similar to this occurs at the hip.  As pictured here, what you see is a retro-trendelenburg.  In this position, you see the athlete subconsciously position their center of gravity (upper body) further laterally which increases body stability (between the acetabulum and femoral head) and requires significantly less MVC of the gluteus medius.  As a practitioner or examiner, if you don’t look for this and you are only looking for adduction in the frontal plane as your indication of gluteus medius weakness, then you may miss an opportunity to not only reduce ACL risk but also risk for a labral tear in the hip.
With severe weakness come severe deviations.  In the knee, this means that adduction in the frontal plane is of such large magnitude that we are also now starting to see significant internal rotation of the femur.  But what does that look like in the hip?  In the hip, this results in a trendelenburg along with a rotation (what we define as a cork screw).  In this scenario, the gluteus medius is so weak that the pelvis drops and rotates at the same time.  Looking at the origin and insertion of the gluteus medius, the muscle is failing through its full range of motion and hence why these two movements occur in unison.  This is most easily observed by the position of the contralateral limb (non-stance leg).  If this leg comes way across midline like this, then there is both a component of hip drop as well as rotation that is occurring at the hip.  In these cases and under high loads (jumping and running) the amount and magnitude of shear stress that is imparted to the labrum of the hip significantly higher than it is intended to take or that it is designed to take.  In this volleyball player pictured here, you can clearly see the trendelenburg and rotation occurring in both single leg squatting motions as well as in single leg hopping motions.  That said, not only is this athlete at risk for ACL injury but also hip injury.  As a practitioner or examiner does not look for this, then they are missing an athlete that is at high risk for injury, especially in sports that require running and jumping. 
Considering all the above, we can now grade our gluteus medius weakness based off the deviations that we see presented at the pelvis as much as what we see at the knee.  At the pelvis, we would expect the following gradients:
  • Trendelenburg – mild/moderate gluteus medius weakness
  • Retrotrendelenburg – moderate to severe gluteus medius weakness
  • Cork screw – severe gluteus medius weakness
Ok, so now we have it but what does all this mean for strengthening? Stay Tuned!
We hope that you found this blog insightful and useful.  Stay tuned next week we will discuss how do we train the gluteus medius in both an open kinetic chain and closed kinetic chain.  As we stated previously, stay tuned and if you like what you see, SHARE THE PASSION!  It is the biggest compliment you can give.  Follow us on Twitter @ACL_prevention and tweet about it.  #ACLPlayItSafe and help us spread the passion.

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 developer of an athletic biomechanical analysis, is an author of a college textbook on this subject  and has performed >5000 athletic movement assessments.  He serves as the National Director of Sports Medicine Innovation for Select Medical, is Chairman of Medical Services for the International Obstacle Racing Federation and associate editor of the International Journal of Athletic Therapy and Training.