Battling Anatomy: Implications for Effective Squatting

Kevin Neeld, CSCS
 

 
Squatting will always be a fundamental movement pattern in everyday activity.  Despite the arguments made my single-leg exercise enthusiasts (including myself), it’s unlikely that there will ever be a time when double leg squatting is removed as a fundamental movement pattern in training programs.  Can you envision powerlifting competitions with one leg squats or Olympic lifting competitions with one leg cleans or snatches.  Me neither.  In an attempt to maximize performance and minimize injury risk, I couldn’t help but wonder about the causes of two potentially hazardous movements I see in a large percentage of the squatting population:

1)   Knees collapsing in

2)   Hips tucking under

The cause of both became very clear to me while sitting at Shirley Sahrmann’s “Diagnosis and Treatment of Movement Impairment Syndromes” seminar this weekend.  Let’s start with the knees collapsing in.  First off, I want to make it clear that I’m not referring to the people that squat like Bambi who initiate the movement with an inward drop of the knee (go into a knock-kneed position).  WIth these squatters, a simple “push your knees out” cue usually fixes everything.  I’m talking about people that are pushing their knees out as hard as possible the whole time, but can’t prevent a slight inward movement of their knees at the bottom of the range-of-motion (ROM).  This issue has something to do with the changing role of the involved musculature.  In a relatively recent article (http://www.t-nation.com/free_online_article/sports_body_training_performance/how_not_to_warm_up&cr=), Nick Tumminello pointed out that the piriformis switches from an external rotator of the femur to an internal rotator of the femur around 90° of hip flexion.  In a not so recent study, Delp et al. (1999) pointed out that the gluteal muscles (maximus, medius, and minimus) also switch from external rotators to internal rotators around the same degree of hip flexion.  This has HUGE implications for this area of the ROM.  Think about all of the other muscles that could potentially contribute to internal rotation of the femur.  The huge mass of adductors also tends to pull the femur into internal rotation while producing force.  Usually this is counteracted by small deep external rotators (piriformis, inferior gemellus, superior gemellus, obturator internus, obturator externus, and quadtratus femoris) and the bigger, stronger gluteal muscles. 

When Dr. Sahrmann presented research pointing out the changing role of the piriformis and gluteal muscles around 90° of hip flexion, it clicked.  The strength balance switches to a situation where only 5 of the deep hip external rotators are functioning to counteract the internal rotation force produced by the adductors, gluteals and piriformis.  In light of the fact that most people have EXTREMELY weak and underutilized deep hip external rotators anyway, it’s no surprise that they would lose this battle.

The implications for training are dependent upon the degree of movement toward the bottom of the squat.  In some cases, a very slight (almost undetectable) movement of the knees is probably okay.  However, if there is an notable inward movement of the knees at the bottom of the squat, it should be addressed before knee and hip problems begin to manifest.  The solution is simple: strengthen the deep external rotators of the hip.  Many of the mini-band and single-leg exercises originally proposed by Michael Boyle serve this purpose well.  A few good ones are:

Lateral Mini-Band Walk

Backward Monster Walk

Side-Lying Clamshells

Supine Clamshells

Side-lying Leg Raise

The issue of the hips tucking under receives much more attention.  Normally this was attributed to short lateral hamstrings.  Last year at Boyle’s 2nd Annual Winter Seminar, John Pallof pointed out that hamstring shortness probably wouldn’t be a limiting factor considering the knees are in over 100° of flexion at the bottom of a squat.  This got me thinking: What else attaches to the hip that doesn’t cross the knee?  That’s simple.  The adductors, and since the adductor magnus also has an attachment to the ischium (near the attachments of the hamstrings), that seemed to be a likely culprit.  That was the theory I ran with for about the last year, right up until I started working with a new client with a background in Olympic and powerlifting.  Take a look at these videos and see if you have the same reaction I did when I first saw him squat.

*Note that in two of the videos he is squatting with special shoes and a wide stance and in the others he has a more narrow stance and is barefoot.

Hopefully you noticed that his left hip continued down about an inch lower than his right.  So what’s the problem?  Unilaterally tight adductors?  Lack of hip “mobility” on his right side?  While I didn’t think it was a modifiable tissue adaptation, I still looked into it.  He also noted that at the same depth that his left hip began to drop down lower, his right leg went numb and weak.  Nerve compression seemed like a logical explanation.  Having spent the Summer reading everything I could on groin pain, sports hernias, and femoracetabular impingement, I had a suspicion that we were dealing with a case of CAM impingement. 

With CAM impingement, the head/neck offset of the femur is decreased.  In other words, instead of having a distinct ball-shaped femoral head, it’s more like a thickened peg extending from the femoral shaft.  During hip flexion, the femoral head rotates within the acetabulum (hip joint).  At a certain degree of hip flexion, the “hood” of the acetabulum slides over the edge of the femoral head and into the femoral neck.  This is the bony limitation to hip flexion.  As you can imagine, if there is no femoral head/neck offset, the acetabulum will have nowhere to slide over the head, and will abut against the thick femoral neck at an earlier degree of hip flexion.  This is also typically accompanied by an impingement of the anteriosuperior labrum of the hip.  This is an ANATOMICAL limitation to movement.  In this individual’s case, it’s a pretty severe, unilateral issue.  However, in many other cases, the anatomy of the hip joint will lead to a similar situation bilaterally whereby hip flexion ends before the “average” 120-130°.  Jeff Oliver spoke about this in a recent strengthcoach.com podcast.  Dr. Sahrmann noted it during her seminar this weekend.  A few months ago, I also spoke with Philadelphia Flyer’s strength and conditioning coach and athletic trainer Jim McCrossin about a similar issue.  All seem to agree that forcing ranges of motion that isn’t anatomically available is moronic. 

This has SIGNIFICANT training implications.  Notably, it is completely ridiculous to say that everyone should squat to the same depth.  Someone with limited hip flexion that attempts to squat deeper than their anatomy allows inevitably tucks their hips under at the bottom.  Invariably this leads to lumbar flexion under a significant load.  Dr. Stuart McGill has identified repeated lumbar flexion (especially in the presence of rotation) as the mechanism for lumbar disc injury.  As I mentioned earlier, this can lead to impingement, wearing, and eventual tearing of the labrum.  These injuries are also related to the early development of osteoarthritis.

I believe that as our understanding of the hip joint improves, we’ll find that some of these impingement injuries aren’t strictly an anatomical abnormality due to genetics, but occur as a result of long-lasting movement impairments.  As an example, the athlete in the video above noted that this restriction in his right hip began within the last couple years.  Referring back to Dr. Sahrmann’s anterior glide syndrome of the hip (whereby the femoral head is anteriorly positioned in the hip joint, creating excessive pressure against the anterior hip joint and limiting hip flexion), it is possible that forcing hip flexion not only creates pressure against the acetabulum, but also on the head and neck of the femur.  Wolff’s law states that bone will respond to the stresses placed upon it.  This leads me to believe that additional stress/pressure placed on the head/neck of the femur may result in additional bone growth.  The additional bone growth could further exacerbate symptoms associated with CAM impingement and lead to an increasingly limited ROM.  Admittedly, research supporting this idea is somewhat lacking.       

If you’re a coach or athlete with an “old school” mindstate and tend to think that everyone should squat “ass-to-heels”, I’m begging you to reconsider.  The reason you may have not heard about these injuries is because our understanding of them is in its infancy.  The majority of the relevant literature has been printed within the last 10 years, and frequently involves descriptions of coexisting pathologies.  One thing is clear: anatomical variation at the hip joint is profound, even within genders.  If two people aren’t built the same, they can’t be expected to move the same.  It’s anatomically impossible. 

There is a relatively simple fix for this hip tucking that can be effectively implemented in one-on-one or team settings.  Box squatting (using the so-called “touch and go” method).  Start the box at a height that allows a full squat depth (top of thigh parallel).  If you see abnormal or undesired hip movement, move them to a higher box.  It’s that simple.  Just squat to a box that’s set to a height above the point of asymmetrical hip movement or hip tucking.   Squatting to a box is another idea I’ve heard Coach Boyle discuss, but didn’t fully recognize the value of this approach until recently.  It builds awareness for the athlete, makes teaching squat depth simple, and can easily be implemented to avoid some of the injuries associated with “abnormal” hip movement discussed in this article.    

My goal was to discuss a couple commonly seen squatting abnormalities and associated ways to minimize injury risk.  I hope I have succeeded in convincing you that assuming that all people should squat with the same mechanics is both dangerous and irresponsible.  It is still possible to improve strength and performance without squatting to full depth.  Take another look at your athletes hips while they’re squatting.  If you see abnormal movement, correct the pattern to stay within their individual anatomical limitations.  They’ll thank you later for keeping them on the field/court/ice and out of the operating room.

References

* Special thanks to Michael Boyle and Brijesh Patel for their assistance in developing many of the exercises presented in this article.

Delp, S.L., Hess, W.E., Hungerford, D.S., & Jones, L.C. (1999). Variation of rotation moment arms with hip flexion. Journal of Biomechanics, 32(5), 493-501.