Let us consider the role in Structural Integration of the group of small but important muscles known as the deep lateral rotators of the hip (Fig 1). Our central argument is that we should include their role as postural extensors of the coxofemoral (hip) joint. The differing role of five myofascial units within the fascia of the posterior hip ? the gluteus medius, piriformis, obturator internus, obturator externus and quadratus femoris ? are considered in this light and treatment strategies proposed for these structures in anterior and posterior pelvic tilt.

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One of the many unique features of human plantigrade carriage is that the femur posturally rests in general coronal alignment with the longitudinal axis of the spine. No other primate, let alone quadruped, is accustomed to such hip extension; all of their mid-range positions for the femur are substantially flexed at 90o to the axis of the spine or more.

Bring the leg of any cat or dog into such full extension; and one is likely to get an unmistakable non-verbal response before reaching the angle required for human standing. One of the features that make the Lipizzaner horses justly famous is their ability to extend their femur in the hip well beyond the normal range, close to that of the human.

Attaining and maintaining this posture, in either phylogenetic or ontogenetic (evolutionary or individual) terms requires approximating the ischial tuberosity (IT) to the femur. Hip extension can involve either extending the femur away from the front of the pelvis, as we just did with our cat, or bringing the posterior aspect of the pelvis closer to the shaft of the femur. Upright standing requires the latter: swinging the pelvis posteriorly around the head of the femur (Fig 2). Coupled with the erector spinae above and the soleus below, the hip extensors are the muscles that stay contracted, predominantly with slow-twitch endurance fibers, keeping us upright for all of our standing hours.

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Fig 2: Human standing requires a powerful movement of the hip bone around the femur to approximate the ischial tuberosity to the femur. (After Molliere)

The hamstrings, pulling directly inferior from the posterior surface of the IT, are usually considered to be the primary hip extensors. These muscles are also facially continuous with both the erectors and the soleus (fellow travelers in the Superficial Back Line(1)-Fig.3). While their role as hip extensors is unassailable, they have two disadvantages in performing the postural part of this uniquely human hip extension:

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1. All three hamstrings are two-joint muscles, flexing the knee as well as extending the hip. This author?s clinical finding is that the body?s brain primarily uses the deeper, single-joint muscles to maintain posture, leaving the more superficial multi-joint muscles to modulate and coordinate movement. How do the hamstrings mediate between their pivotal postural and movement roles?

2. All the hamstrings are very long. Because of the linear alignment of myosin and actin elements, maintaining posture via such long muscles (despite the extensive membranes and tendon arrangements within them) is mechanically and physiologically disadvantageous.

Which are single joint muscles whose tonus might maintain human hip extension against the force of gravity, the tension in the numerous hip flexors, or the elastic recoil of the pubofemoral ligaments?

In answer, we find the long portion of the adductor magnus, a single-joint muscle of the hip just deep to the hamstrings, and the deep lateral rotators (Fig.4). In fact, every one of the muscles behind the coronal midline of the femur can help extend the hip: in addition to the posterior fibers of adductor magnus, we can include portions of the gluteus medius and gluteus minimus, piriformis, gemellus superior and inferior, obturator internus, and quadratus femoris.

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Fig 4: The adductor magnus assists the hamstrings and the deep lateral rotators in maintaining hip extension. Art courtesy of John Hull Grundy, used with permission.

This list constitutes the posterior portion of what can be seen as a “fan” of muscles, or a set of spokes around the “hub” of the greater trochanter.(2) The tensor fasciae latae, and anterior portions of gluteus medius and minimus constitute the anterior ? and thus hip flexor – part of this fan.

The fact that these muscles are commonly named the “deep lateral rotators” (of the femur) demonstrates that their role as extensors of the hip has been under-appreciated in our consideration of hip biomechanics. The name implies that the pelvis is the origin and the greater trochanter of the femur is the insertion. For the remainder of this article, we will be reversing the emphasis, taking the femur as origin and the posterior aspects of the os coxae as the insertion ? hence extensor coxae brevis.

Though the two tasks of lateral femoral rotation and hip extension are related (think of roller blading or skating, and by extension, walking), their role as lateral rotators is subordinate, in this writer?s opinion, to their postural role in the maintenance of hip extension in upright posture.

If we recognize their role in hip extension, these muscles become crucial to any strategy for dealing with an anterior or posterior pelvic tilt, as these postural positions could be alternatively described as hip flexion and extension respectively. In hip flexion / anterior pelvic tilt, these muscles will be eccentrically loaded (locked long); in hip extension / posterior tilt, they will tend to be concentrically loaded (locked short).

Both of these positions involve a functional weakness in terms of the muscle?s ability to generate forceful contraction on any attachment or across the hip joint itself. Eccentrically loaded muscles have less overlap between the myosin and actin proteins, and thus cannot generate a strong contraction. Concentrically loaded muscles have plenty of overlap (so it is more difficult to generate relaxation in them), but are so near the end of the “ratchets” that they cannot generate significant further contraction. Even though there is a certain amount of adjustability in tonal length within the muscles, neither of these extreme positions makes for efficient and strong muscle contraction.

<center>Pelvic tilt and pelvic neutral</center>

If the treatment strategy varies with pelvic tilt, how do we determine pelvic neutral? Opinions abound as to what constitutes a neutral pelvis. Ida Rolf suggests that when the superior surface of the pubic bone and the tip of the coccyx are in horizontal alignment, the pelvis is in a proper neutral.(3) Kendall and McCreary posit that pelvic neutral is when the ASIS and the front surface of the pubic bone are in coronal alignment.(4) Others have suggested an angle of 16 degrees from the horizontal between the ASIS and PSIS.(5)

This author finds any of these markers objectionably geometric and unnecessarily fixed, as they fail to account for the dynamic relation between the femur and the lumbar spine through the pelvis. We have been using a more individually responsive test, which has its problems, but produces, in our opinion, a truer result than simple geometric measures.

With the client in relaxed standing, place your hand ever so gently on their head, with a cranial touch ? no more than a nickel?s worth of pressure. Resting in the hair will suffice to feel what you are looking for. From whatever pelvic position is “normal” for the client, have them tilt the pelvis a bit anteriorly. Does the head rise into or shrink away from your hand? If they keep tilting the pelvis forward, at some point the body will shorten away form your hand. Have them return to their normal. Now have them tilt the pelvis posteriorly a little. Same question: does the head bloom into your hand or shrink away? Again, if they continue into posterior tilt, the spine will eventually shorten away from you.

In this model, pelvic neutral, the postural ideal is when the head is at its highest, indicating that the spine is at its longest. The operating principle for this test is that the pelvis should rest in the position where the spine is “living its full length”.

Have the client repeat in each direction a few times to make sure you are reading the results correctly. This test is more accurate the more differentiated and integrated the client is, so that they can isolate the movement of the pelvis from compensatory movement in the legs and lumbars. In clients who are challenged with excessive stiffness, injury, or surgery, the test may show mixed results. In most cases, however, the anterior or posterior tilt of the pelvis reveals that “highest point”, and that is where you should aim for having the client rest in normal. Please note that we are not suggesting that you should instruct the client to “put” themselves in this normal; if you do good work, the client will arrive naturally and without effort at this normal.

<center>Anatomy</center>

A brief review of the anatomy will be helpful before discussing treatment options. Precise palpation directions are offered, as all of these muscles lie deep to the large and thick gluteus maximus. All but a small portion of this muscle is quiescent in standing, so its role in hip extension is limited to running and stair-climbing, and not, like the rest of this list, in pelvic posture. We proceed from superior to inferior.

Gluteus medius, posterior portion ? The posterior portion of the gluteus medius is a combination of a hip extensor and abductor, and is a purely appendicular muscle. The posterior edge of this muscle is a distinct slip running on the oblique line between the posterior superior iliac spine (PSIS) and the superior aspect of the greater trochanter. By strumming across this line, the trailing edge of this muscle can usually be distinctly felt.

Piriformis ? The only two-joint muscle of this group, as it also crosses the sacroiliac joint, passing from the top of the greater trochanter through the greater sciatic foramen to attach to the anterior aspect of the middle three segments of the sacrum (Fig 5). The piriformis is thus the sole axial-appendicular muscle of this group, with the ability to create “force closure” on the sacroiliac joint during gait. This function, combined with its contribution to stabilizing the sacrum at the bottom of the spinal “lever” in lateral tilts, bends, and rotations, stretches the poor piriformis among multiple roles.

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This muscle can be most easily palpated in the center of a triangle made from the top and bottom of the sacrum along the midline and the posterior aspect of the greater trochanter. Strumming up and down over the center of this triangle will often (but not always) reveal the small but potent piriformis. Whether it can be distinctly felt or not, this is where piriformis is most easily affected manually, given that access via the anus is beyond the scope of practice of most readers.

Gemellus superior ? This small muscle passes from the lateral end of the sacrospinous ligament to the trochanteric fossa, and can thus provide muscular reinforcement to the ligament in its role of stabilizing the side-to-side movement of the sacrum. In this way, this muscle is, in effect, a two-joint muscle as well, helping to reinforce the sacroiliac joint via the sacrospinous ligament. Palpate this muscle along with obturator internus.

Obturator internus ? This fascinating muscle also inserts into the trochanteric fossa, passing behind the ischium to take a 90 degree turn over a bursa, fanning out to cover the whole inside of the lower flange of the hip bone within the true pelvis, completely covering the medial side of the obturator membrane. This muscle is thus much larger and stronger than it looks from a posterior view of the hip. It also provides an attachment to the iliococcygeus of the pelvic floor. Take these two muscles together on both sides, and one can see a fascial “hammock”, strung from trochanter to trochanter under the hip joint. In the view of some anatomists, that complex can provide a resilient “spring” for the forces transferring from the spine to the legs (Fig 6).

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To find the obturator internus (OI), locate the ischial tuberosity (IT) from below on your prone client. “Walk” your fingers up the “mountain” of the bone toward the head until you find a soft “meadow” of muscle ? this is the OI. From here go directly lateral to find the distal tendinous portion of this muscle, which may blend with one or both gemelli to produce a single large tendon, or may remain palpable as two or three distinct tendons.

To find the larger, internal, and more muscular proximal part of OI requires courage and a willing client, but place three fingertips just inside the IT, using the sacrotuberous ligament as a guide for the index finger. Slide in the direction of the navel, lateral to the anal verge. Your finger pads will feel the IT / ischial ramus at first, but as you pass into the ischio-rectal fossa, you will encounter a softer area that is comprised of the lower fibers of OI. You will be stopped in your upward progress by the pelvic floor, which crosses over from the midline to attach to the OI fascia at the arcuate line.

Gemellus inferior ? This small muscle reinforces the obturator internus from below, extending from the distal end of the sacrotuberous ligament on the ischial tuberosity to blend in its attachment with the tendon of the obturator internus. Though this muscle shares with all the others in this list the roles of hip extensor and lateral rotator of the femur, any additional role ? such as providing an adjustable reinforcement to the sacrotuberous ligament ? is unclear.

Quadratus femoris ? The last but not least of our group extends from the lateral aspect of the IT straight laterally to the posterior trochanter. This muscle is a powerful postural extensor of the hip (or, more accurately, a powerful resistor to hip flexion), given its ability to approximate the IT to the posterior aspect of the femur, and will be short and bunched in most clients with a pronounced posterior tilt.

Because the muscle is quadrate, it rarely presents as a twangy bit of myofascia, but more often as a mound of tissue. Quadratus can be found and assessed above a line lateral to the lower end of the IT. This is frequently above the line of the superficial gluteal fold. The similar mound more distally located on the femur, below the gluteal fold, is the fleshy attachment of the gluteus maximus.

Obturator externus ? This muscle is usually included in the deep lateral rotator group, but is not an “extensor coxae brevis” because it acts ? alone in this group ? as a hip flexor. This rogue muscle is hard to palpate and difficult to treat in its entirety. Originating from the outer surface of the lower flange of the hip bone, covering the outer surface of the obturator membrane, passing under the neck of the femur from anterior to posterior, to attach into the trochanteric fossa deep to the quadratus femoris (Fig. 7).

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Obturator externus (OE) counterbalances the OI in hip flexion and extension, though both combine to resist the medial rotation of the femur. It also offers a muscular reinforcement to the neck of the femur when it is under extra strain (in landing after a jump, for instance). It is probably not a powerful hip flexor, given the competition it finds in the iliacus, pectineus, and rectus femoris, etc., but chronic shortness in its myofascia prevents the ischial ramus from moving forward and the pubic bone from lifting.

<center>Treatment</center>

Having come this far, treatment options abound. The one sentence précis is that in cases of anterior tilt, the fascia of this muscle group needs to be taken inferior, while in cases of posterior tilt these myofascial units need to be released and allowed to reset at lower tonus.

In anterior tilt, these muscles will be eccentrically loaded, so any or all of them may present as twangy, tight, and sore with active trigger points. In posterior tilt, they will frequently present as bunched, often seemingly tied together, but only with passive trigger points.

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<i>Posterior tilt ? Fig.8</i>

In posterior tilt, a variety of treatment options may be used to reset tonus, including active isolated stretching, strain-counterstrain, or proprioceptive neuromuscular facilitation. In terms of more commonly-used Structural Integration techniques, working along each individual muscle from pelvic origin toward the femoral insertion, using the guidelines for specificity outlined above.

The posterior edge of the gluteus medius is easily located between the superior trochanter and the PSIS. Beneath this muscle, the harder-to-feel but equally potent gluteus minimus can be contacted (usually to the client?s initial horror) by passively abducting the side-lying client?s leg with one hand or forearm, while working deeply into the posterior hip with the other elbow.

The piriformis is harder to locate on some clients, but following the direction to the center of the triangle described above will guarantee that you are on the piriformis whether it can be detected or not. Work laterally and inferiorly toward the insertion to lengthen this muscle (at least temporarily ? modulating pelvic tilt is only one of piriformis?s many roles, which include antagonizing the lower psoas over the sacroiliac joint, reinforcing the sacrospinous ligament, and preventing excess movement in the sacroiliac joint due to forces descending from spinal movements above.)

Gemellus superior and inferior are usually addressed with the obturator internus rather than individually, again working laterally along the muscles from the lateral side of the upper ischial tuberosity toward the fossa at the back of the greater trochanter. Work deeply and slowly for best results.

For the intrepid practitioner and the willing client, the portion of OI can be reached by sliding the fingertips up into the ischiorectal fossa in the direction of the navel, using the sacrotuberous ligament as a guide. Once onto the muscular fibers of the OI proper, hook the myofascia and bring the issue inferiorly and posteriorly, as the client medially rotates the femur. This one technique can result in a substantial reorientation of the pelvis in the direction of an anterior tilt, restoring a proper lumbar lordosis.

The quadratus femoris is a tough piece of myofascia that can be worked quite hard and needs to be worked quite thoroughly in these cases, mostly along the back side of the trochanter superior to the gluteal fold. Release of this muscle often results in the ability to more properly fold the hip joint into flexion.

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<i>Anterior tilt ? Fig.9</i>

For anterior tilt, the entire set of myofascial units needs to be pulled caudad. This can be accomplished most easily behind the trochanter, where they all terminate. Hook the fascia with an elbow at the top of the trochanter and bring it down ? slowly, firmly, deeply – along the back of the trochanter. Several passes and significant weight are often required to effect a change. Similarly, hook tissue along the posterior iliac crest, just lateral to the PSIS, and bring your elbow slowly down along the lateral lower sacrum and ischial tuberosity.

Work across the fibers of the muscles themselves can also be helpful, oblique to the fiber direction to break up longitudinal cross-linkages and stimulate the muscle spindles to return the muscle to a shorter resting length.

Of course, this work needs to be accompanied by the release of the hip flexors and spinal extensors for best results. Including the OE, the renegade of our group, can be helpful in this regard. Again, this requires a willing client and a certain skill by the practitioner.

With your client supine and the knees up, sit next to her hip and cup her knee in your axilla. Find the obvious adductor longus tendon in the groin and place your thumb just lateral to its junction with the pubic bone. Insinuate your thumb between the adductor longus and the pectineus. OE lies deep to these two, and is usually distinctly harder than the pectineus, and deeper than the adductor longus. Contacting it will often elicit a surprised reaction from the client, but with sensitive communication, you can get a release from the portion of the muscle you can touch, which is by no means all of it.

This is only one access point to a fairly large attachment, but by changing the angle of the thumbprint slightly, superior and inferior, lateral and medial against the pubic bone, and calling for a slow pelvic rock, more of the muscle belly can be contacted. Most clients with a fixed anterior tilt will find more freedom after this release, which can be repeated as often as time (and the client) allow.

In cases where the two innominates are in a different angle, the two sides will require different degrees of treatment, but in general, the inclusion of these “extensori coxae brevi” in your treatment plans for excessive anterior or posterior pelvic tilt will be rewarded.

Endnotes

1. Myers, T Anatomy Trains, 2nd ed. 2008 Churchill Livingstone, Edinburgh

2. Myers, T Fans of the Hip Joint, from Body3, self published 2004 and available from www.anatomytrains.com

3. Rolf, I Rolfing 1977, Healing Arts Press, Rochester, VT, p. 87

4. Kendall, F and McCreary, E Muscles, Testing and Function, 3rd ed. 1983, Williams & Wilkins, Baltimore, p.25

5. Shamberger, W. The Malalignment Syndrome, 2002, Churchill Livingstone, Edinburgh