Dooley Noted: 5/17/2015
The deep six lateral hip rotators are a fascinating group of muscles.
They are so deep and perplexing that even researchers aren’t quite sure what they do in every plane.
Regarding concentric load: The biomechanical authorities tend to agree that these 6 muscles lateral rotate the femur, relative to the hip if it’s already extended. These muscles (except for quadratus femoris) abduct a femur, if the hip is in flexion.
These muscles lay deep to a massive superficial gluteal muscle – gluteus maximus.
Even more buried is the most anterior of the lateral rotators: obturator externus (OE).
OE traverses from the anterior parts of the pubis and obturator membrane to the femur’s trochanteric fossa.
The majority of this muscle lays anterior to the quadratus femoris (QF), forcing anatomists to cut through QF in order to see OE from the back.
So instead, we head to the front.
In the femoral triangle, OE lays deep to pectineus. These two muscles tend towards external rotation and are both wired more towards flexion phases.
This is due to their locations and their shared innervations by the posterior division of the obturator nerve. This nerve forms from anterior divisions of ventral rami L2-L4.
What does this mean for you? A few very important things.
1. When palpating this muscle, palate it from the front, not the back. Your odds of proprioceptive input and palpation are much greater from the front where you are going through a half inch of tissue, not potentially 5-8 inches of tissue.
2. If the muscle is wired for more flexion phases, it will work with more anterior chain events. Thus, OE will tend towards wanting to work with quads and adductors in its short phase.
3. When this muscle is locked long, it will contribute to hip compression. Since the muscle travels from the anterior outer pelvis posteriorly to the greater trochanter’s inner fossa, it works as a sling with obturator internus to keep that femur jammed into the acetabulum.
This is lovely when the hip needs compressed, such as when weight bearing on a lead leg during the suspension phase of gait. It becomes problematic when one wants to hip extend and laterally rotate – and these muscles are stuck in a locked long position.
You end up with symptoms of hip compression, like reduced ability to laterally rotate, coupled with the “C” sign – pain in both hip pockets, rotating like a letter “C” from front pocket to back pocket.
So, if you are having chronic hip pain, get assessed for OE and its lateral rotator pals being dominate at the hip.
It’s fascinating to think a muscle as large and powerful as gluteus maximus can be overridden by the tiny OE, but it’s absolutely probable in cases of hip compression.
If you have large buttocks patients (like myself), you’ll have an easier time palpating OE from the front.
Look at that anatomy, and head towards the femoral triangle to palpate it just deep to pectineus.
Caution: if you feel a pulse, GET OFF of it. That’s the femoral artery. Go deep and medially, closer to the pubic body.
Rethink the OE, its functions, and its location.
As always, it’s your call.
– Dr. Kathy Dooley
