The Mysteries of the Sacrum Revealed

By Lina Amy Hack, Certified Advanced Rolfer® and Jan H. Sultan, Advanced Rolfing® Instructor
January 2024

ABSTRACT For years, Jan H. Sultan, Advanced Rolfing® instructor of the Dr. Ida Rolf Institute®, has been developing a coherent approach to the mysteries of the sacrum from the structural integration perspective. In this interview, Sultan gives insight into some of the biomechanical and physiological movements of the sacrum and a few suggested applications to resolving common strain patterns in the low back region.

Lina Amy Hack: Hi Jan, for this article, we will narrow our focus to discuss the human sacrum and a few insights into the Rolfing® Structural Integration point of view when working with the sacrum. What should we keep in mind when focusing on this vital junction of the lumbar, sacrum, and ilia?

Jan Sultan: The first thing we have to do is go to embryology and look at the fact that when the spine develops, the sacrum is laid down as part of the spine. Fundamentally the sacrum is made of five fused vertebral segments, and in addition, there is the coccyx, which has its own synovial joint with the sacrum and is comprised of a couple of rudimentary vertebral segments articulating from the end of the sacrum. So, unequivocally, the sacrum belongs to the spine (see Figure 1).

The second thing is that the ilia belong to the legs. Embryologically, the acetabular space is where the innominate (coxal) bone and femur develop together. This puts the ilium, the ischium, and the pubis together, operating with the femur as a leg; this innominate-femur unit relates to the sacrum (see Figure 2). In this view, the sacrum is only part of the pelvis as the ilia relate to it, and together they create this relatively stable bony ring. This structure we call a pelvis is the bowl holding the viscera from below, as well as a locomotor center, with motion at the pubic symphysis and the innominate articulating on the sacrum as the sacroiliac joint (see Figure 3).

This is the root understanding of the sacrum that you must have to carry forward in your inquiry: In one sense, there is no pelvis; there is a meeting place of components, of different systems coming together. It is a transition point between the innominate bones belonging to the legs and the sacrum belonging to the spine. Where they meet and create this discrete structure, there you have a pelvis.

LAH: The sacrum is part of the spine. Would you include the skull?

JS:  There is another whole domain of sacral movement in addition to the locomotor functions. There is the physiological motion of the craniosacral system (also known as the primary respiratory mechanism, PRM) that embryologically develops with the skull and vertebral column (Upledger 1983). This extends to and has continuity all the way to the sacrum. This is known as the craniosacral system, which is complete with the cerebrospinal fluid, the dura, the meninges, the bones of the neurocranium, all twenty-four vertebrae inclusive of the spinal cord, and the sacrum. These elements meet the ilia at the sacroiliac joint (SI joint), which is itself a foundational place for the locomotor system of the legs (Gracovetsky 1988).

So, right at the sacrum, we have the primary respiratory mechanism of the craniosacral system and the kinesiology of locomotion, sharing the same space-time and the same structures (see Figure 4). This makes for an interesting therapeutic consideration. Much of human bipedal upright dysfunction happens around the sacroiliac, pubic symphysis, and lumbosacral regions. It points to using this understanding (of the nature of structure) to help people resolve these strain patterns and to function at a higher level.

LAH: Okay, wow. I don’t think I’ve considered these two things at the same time. Let’s break it down – how are we to understand the workings of these two motions that happen at the sacrum?

JS: Think about how the two SI joints look like the letter ‘C’ opening posteriorly (see Figure 5C). Since the ilium is part of the leg, the behavior of the SI joints makes sense. The ilium articulates on the sacrum in various ways while walking. Generally speaking, when the leg is load bearing and pushing off the ground, the same-sided ilium rocks forward in relation to the sacrum. When the leg is swinging under the body, the ilium rocks back on the sacrum. In a well-functioning body, the biomechanical activity of the legs does not heavily load the sacrum but rather articulates with it, leaving the function of the sacrum and the spine intact.

Figure 1: The spine is divided into four regions: the cervical, thoracic, lumbar, and sacral bones. To understand the sacrum is to see it in context with all the vertebrae. The sacrum and the thoracic spine have a primary kyphosis, and the lumbar and cervical spine have a secondary lordosis. The magnitude of these curves varies greatly between individuals. Copyright Thieme Medical Publishers Incorporated, 2023.

LAH: When I’m working with a client’s sacrum, one of the first investigations I make is to figure out their individual sacrum’s shape. From there, I work to infer their sacral position and functionality. Is that a good starting point?

JS: Yes! Sacral shape considerations are the next step in recognizing that the sacrum is part of the spine and the ilia are part of the legs. There’s a lot of variation in sacral shape (Nastoulis et. al 2019). Years ago, I was visiting the Smithsonian Museum of Natural History, and they had a lot of bones on display at that time. I went to one of the docents and asked to see their archived bones, the sacra in particular.  

In the archives, there were big drawers that were approximately four feet wide and a couple of feet deep. Inside each drawer, there were about twenty sacra, each one had a write-up about where they had come from. There were sacra from everywhere in the world, from the people of the North, people of Africa, Native Americans, and Aboriginal peoples from various continents. It was difficult to see this collection because these bones were removed from Indigenous graves and likely taken without consent.

Archaeological politics notwithstanding, it was a profound learning experience. What was so evident was the variety of sacral shapes. They varied in two particular ways. When seen in profile, some sacra were rounded like an arc of a circle, while other sacra profiles were quite vertical. When looking at the anterior aspect, some were relatively oblique and broad, like an equilateral triangle, while others were acute and narrow, standing tall. There were many drawers of sacra, and the variety was phenomenal. By extension, the sacral shape would have a huge impact on how the person’s pelvic contour would look posteriorly and while walking, going about their normal activities. For some people with less sacroiliac mobility, their sacrum behaves like part of the pelvis. In other people, the ilia truly articulate on the sacrum. These variations represent, more or less, the complexity of movement crossing the sacral region.

Figure 2: The innominate bone relates to the sacrum yet belongs to the leg. (A) The femur rests in the acetabular space, which is a junction of the triradiate cartilage of the ilia, the ischium, and the pubis coming together. (B) The ilium, ischium, and ramus bones that make the acetabulum do not complete their developmental fusion until mid-puberty (11 to 15 years in females and 14 to 17 years in males), “with the pelvic surface generally fusing before the acetabular aspect” (Verbruggen and Nowlan 2017, 646-647). Copyright Thieme Medical Publishers Incorporated, 2023.

LAH: How would the muscles be different with these variations?

JS: The gluteal muscles can function like short hamstrings for a relatively vertical sacrum, and as such, this limits the power of the gluteal muscles. Compared with a much more curved sacrum, the higher amplitude curve would give a very different platform for the gluteal muscles to draw the femur posterior into extension. In this case, the curved sacral shape can lead to gluteal muscles functioning with a broader reach like both hip and leg extensors.

Consider that the gluteal muscles and the psoas are in relative reciprocal tension, and the sacrum is sandwiched between them. When the gluteal muscles are firing for the extension of the hip, the psoas eccentrically allows length. When the leg is swinging forward and about to place the foot down for forward walking, the psoas is concentrically contracting and the gluteal muscles are eccentrically allowing length. This reciprocity is part of the normal walking pattern.

If you consider these structures in a quadruped, this pattern makes total sense. Take horses, for example, they have a horizontal spine inclusive of their sacrum (Van Weeren 2012). Their relatively vertical hind legs are beneath the sacrum. As their back legs flex forward to walk, to prepare for contact with the ground, the gluteal muscles have to be lengthening, and the psoas is shortening. Then, the power stroke of walking forward happens where the psoas reciprocally gives up length and the gluteal muscles shorten; this delivers the force that propels the animal forward. The gluteal muscles and the psoas are modulating in relation to each other, they’re firing in a reciprocal tension system. Not an on/off agonist/antagonist pattern but rather a relatively eccentric or concentrically contracting system as power is needed.

Figure 3: Anterosuperior view of the pelvic girdle, with the two innominate bones (coxal bones) and L5 meeting at the sacrum. Here we can see the distinction between the lumbosacral and ilio-pubic parts of the pelvis. Copyright Thieme Medical Publishers Incorporated, 2023.

LAH: How does that relate to the human animal with an upright spine?

JS: The huge difference is that the quadruped has a relatively broad base while standing on four legs. In a human, you’ve got a narrow base and a height that is five to ten times as tall as the stance is wide. As bipeds, our calcaneus acts like the back leg, and the forefoot is your front leg. This frees the arms to go someplace else, to get into all the mischief humans create in the world. Also, in the quadruped, the sacrum doesn’t necessarily get recruited as a weight-bearing unit. At the same time, in a biped, it is very easy to have sacral strains show up as motion restrictions that influence the function of the whole spine. So, the quadrupedal sacrum is actually more stable than a bipedal sacrum by nature.

Figure 4: The sacrum is moved by both the physiologic motion from the cerebrospinal fluid production and absorption and biomechanical motion of walking.

Conversely, a bipedal sacrum has to fine-tune the SI joint where the ilium can actually articulate on the sacrum and the spine can stay more or less in the midline. Those two SI joints are synovial joints enveloped in a fibrous capsule. They act kind of like sacral waterbeds, which indicate a design for movement. There is some controversy about sacral mobility, and some orthopedic textbooks refer to the SI joint as completely motion restricted. But the presence of a synovial joint belies that conclusion. In function, the SI joints are somewhat vulnerable to becoming motion restricted through atypical movement dynamics, like adaptation to a foot or leg injury or from strain coming from higher up in the body and crossing the sacrum from the upper body into the innominates to the lower body.

Figure 5: The sacrum is formed from five postnatally fused sacral vertebrae. The superior aspect of the sacrum articulates with the fifth lumbar vertebra and the inferior aspect articulates with the coccyx. In the lateral view, the articular surface of the SI joint appears like the letter ‘C’. Copyright Thieme Medical Publishers Incorporated, 2023.

LAH: So then, let’s get more specific. What is normal movement at the sacrum?

JS: Well, as you can see, I’m putting forward the argument that sacral movement roughly divides into two categories: physiological movement of the primary respiratory mechanism, also known as the craniosacral rhythm, and the biomechanical movement of locomotion. So, it depends on which movement you are interested in.

Let’s first consider walking. Walking is a combination of side-to-side movements of the spine, lateral shortening and lengthening like a lizard climbing a wall (see Figure 6), and front-back locomotion movements of the leg propelling us forward. These are the broad biomechanics of the gait. For example, in normal walking, when the person is load-bearing on the right leg, at this moment the thoracic spine will move over to the right, toward the weight-bearing leg. Think of roller skating or skiing, the upper body leans over the foot that has contact with the ground. When you’re standing on one leg, you have translated your upper body mass over the load-bearing leg in that coronal plane. Just like the lizard climbing the wall, in that translation, the sacrum will sidebend a little bit away from the load-bearing leg.

That’s what sets up a lateral lumbar curve to be concave to the load-bearing side. At the same time, the thoracic spine is convex to the load-bearing side, and that’s how the weight of the thorax gets over the leg. So, in normal function, the sacrum sidebends away from the load-bearing leg, setting up the lumbar sidebend. If you could put two points of light on the lateral-posterior edges of the sacral base and have that person walk away from you, then you would see each light going up and down – up when loadbearing and down when unweighted.

Another set of biomechanical sacral movements involve the sacral action when the whole body is forward bending or back bending. The ‘C’ surface of the sacral joint has characteristic movements when reaching upward and arching posteriorly into a back bend. The pressure on the sacrum is to rotate around the SI joints, taking the sacral base deeper into the body relative to the neutral standing position (see Figure 7). By the same token, in a forward bend, the sacral base moves posteriorly, relative to standing in neutral. So, the sacral base has a biomechanical forward-bending and back-bending pattern based on the orientation of the whole spine.

When we look at our clients walking, we ask ourselves, where is the weight-bearing load going onto that sacral base if the sacrum able to move in all these directions? These types of questions lead us to understand individual differences between the basic biomechanics of the sacrum.

Figure 6: When walking with natural contralateral motion, the right arm will reach forward when the right leg completes a step. Part of this movement is in the coronal plane, where the lateral sides of the torso lengthen and shorten like a lizard climbing a wall.

LAH: Right, the basics being back-bend, forward-bend, and the mechanics of walking. And then, what is the physiological movement of the sacrum, given the biomechanical movement?

JS: The sacrum has intrinsic motion that reflects the pressure changes associated with the circulation of cerebral spinal fluid (CSF). This fluid is produced deep in the skull and can be found within the entire spine, including the sacrum. CSF is “a clear, colorless ultrafiltrate of plasma with low protein content and few cells” (Di Terlizzi and Platt 2006, 422). CSF protects brain and spine neural tissue from mechanical damage, it is a brain interstitial fluid filtrate produced in the cortex. The large lateral ventricles within the left and right hemispheres of the brain are filled with CSF, and this is also where CSF is produced [at the choroid plexus epithelium and ependymal cells of the ventricles (Killer 2013)]. There are cyclic pressure changes within the ventricles of the brain and spinal cord due to the production and absorption of CSF (Upledger and Vredevoogd 1983). Of note, the production of the CSF is cyclic while the downstream absorption into the veins is constant. The outer membrane containing CSF is the arachnoid layer and the CSF is found between it and the pia mater, within the subarachnoid spaces.(Hladky and Barrand 2014).

The sacrum has intrinsic movement associated with the expansion and retraction aspect of CSF production and absorption. CSF flows from the lateral ventricles where it is produced, through the extensive subarachnoid spaces, and eventually down the spinal cord, where one of the outflow pathways of CSF is located at the sacral spine into the region’s lymphatic vessels (Ma et al. 2019). And also, there are tethers (denticulate ligaments) within the CSF system anchoring and supporting the contained membranes to the bony vertebral canal and sacral bone.

Figure 7: (A) When a person does a back bend, a spinal extension, the base of the sacrum moves deeper into the body, relative to their neutral standing position. (B) As a person forward bends, into flexion, their sacral base moves posteriorly relative to their neutral standing position.

LAH: I like to think of it as a slowly pulsating river, on the microscopic scale.

JS: The original description of the CSF-associated cranial motion came from William Garner Sutherland, DO (1873-1954), and he called this physiological motion the body’s primary respiratory mechanism (Sutherland et al. 1998). He talked about  this in his book, The Cranial Bowl (1939), and his description was centered around the movement of the sphenobasilar junction of the cranial base, where the occiput and sphenoid meet. Sutherland described the primary respiratory mechanism at the bony level as the flexion and extension of the sphenobasilar junction, as viewed from below. The production of CSF would be responsible for the expansion of the cranial bowl resulting in a decreasing inferior angle [the underside of the cranial base] between the occiput and sphenoid - flexion. CSF absorption was associated with the retraction of the cranial bowl, whereby the sphenobasilar joint would increase in angle – extension. By palpating this rhythm at the sphenoid and occiput, Sutherland reported that this oscillation occurred about twelve cycles per minute (Bordoni et al. 2020).

Now, consider the side view of the SI joint. At the level of S2, you see it is essentially the apex of the backward-facing ‘C’ at the articular arms of the SI joint. When the choroid plexus of the ventricles in the brain produces CSF, the volume of the fluid in the skull is increasing, and the pressure is on those ventricles, and as mentioned, this results in the expansion of fluid volume within the cranium (Rasmussen and Meulengracht 2021). John Upledger, DO (1932-2012) followed Sutherland’s nomenclature and also called this increased pressure and the subsequent movement of the cranial bones the flexion phase of the CSF rhythm. Note that I prefer the term expansion used by Jean-Pierre Barral, DO, PT to describe this phase of the craniosacral rhythm (Barral and Croibier 2009). The expansion (flexion) of the cranium from CSF production rocks the occiput posterior and inferior. By virtue of the dura attachments on the sacrum, expansion draws superiorly on the sacrum to move the sacral base posteriorly, pivoting at that S2 apex associated with the horizontal axis between the two SI joints (see Figure 8).

Figure 8: Sacral motion during the expansion and retraction phases of the craniosacral rhythm; cranial expansion correlates with the sacral base rotating posterior, while cranial retraction is paired with the sacral base rotating in an anterior direction.

At the peak of cranial expansion (flexion), CSF production stops, and a wave of CSF absorption flows to the arachnoid space and into various lymphatic pathways and spinal cord capillaries. As the CSF system pressure diminishes, there is less fluid within the CSF system. Upledger followed Sutherland’s sphenobasilar junction movement reference point and called this the extension phase of the craniosacral rhythm. But for this discussion, I will use Barral’s term, the retraction phase of the CSF rhythm (Barral and Croibier 2009). In the retraction phase of the craniosacral rhythm, the posterior aspect of the occiput moves superiorly. There is a release of the pull on the dura at the sacrum concurrently with that retraction of fluid volume. This releases the cephalad pull on the deep fascia around the spinal cord. And in response, the sacral base rocks anteriorly.  

This is the innate physiological movement (primary respiratory mechanism) of the sacrum, and it is part of the craniosacral expansion/retraction circulation of CSF. With a listening hand, manual therapists can easily feel this intrinsic rocking of the sacrum around the horizontal axis, if the body is in a neutral position. As I sit here at my desk, my sacrum is quietly rocking away as these waves ebb and flow. This sacral movement happens on a horizontal axis that is roughly at the S2 segment, at the apex of the two arms of the SI joint.

So, what we have at the sacrum is a meeting between this physiological movement within the spinal axis and the biomechanical movement that’s coming through the ilia as a component of locomotion. The two share the same space-time moment.

LAH: That is a lot to consider all at once when we are body-reading our client’s form.

JS: As Rolfers, we look at our clients walking, and are taught to observe, then palpate what is happening to the normal sacral movement. What happens to the horizontal
of the sacral response to CSF pressure changes when they are walking? What happens when they are standing? When their load-bearing leg hits the ground, does the sacrum sidebend a little bit away from it?

In walking, sacral motion patterns are completely different than in neutral, and they orient around different axes of motion. As the right leg is load-bearing, the sacrum left sidebends, and the motion orients around a 'transitory diagonal axis' running through the upper arm of the right-side sacroiliac joint and the lower arm of the left sacroiliac joint (Mitchell and Mitchell 1995). During locomotion, the motion will transition back and forth between right and left transitory diagonal axes, while still maintaining the primary respiratory mechanism of the craniosacral system's physiological motion (see Figure 9).

Figure 9: In normal walking, the sacrum alternates between left sidebending and right sidebending, moving around the transitory diagonal axis.

So, in normal walking, sacral motion shifts with its sidebending into transitory diagonal axes. The sacrum maintains its physiological expansion and retraction movements as a reflection of the internal rhythm of CSF production and absorption. The physiological movement of the sacrum at rest shifts from motion around a horizontal axis onto a transitory diagonal axis, while the expansion-retraction motion continues to chug along as you walk. It's beautiful.

The sacrum demonstrates a complex coming together of these movements, and in a well-functioning system, locomotion should not interfere with physiology. A well-balanced sacrum will continue its physiologic movement while the person is in motion.

LAH: That is nice clarity you have woven together there. Can you give us a few more details about this sidebending sacral motion?

JS: Let’s go back to our walking example, where the person is load-bearing on their right leg, their sacrum is sidebending left, away from the load-bearing leg, and the thorax will move over the load-bearing leg because that’s how you balance on one foot. For this to happen, the lumbar spine has to right sidebend, becoming concave to the weight-bearing leg, and the thorax is convex over the weight-bearing leg.

Now, at this point, we need to be concerned with how the L5-S1 junction is behaving when the sacrum sidebends. The fifth lumbar has to respond biomechanically to the transition between the sacral left-sidebending and the lumbar right-sidebending over the loadbearing right leg. That puts L4-L5 and L5-S1 as the focal point of this movement/moment. In normal walking, we have alternating load-bearing going back and forth. This demands a counter-rotating motion at L5-S1 over and over again. While this is millimeters of movement in those tissues, any stress is multiplied with repetition and, with the involvement of local spinal nerve outflows. This creates a potential vulnerability. The spinal nerves have to floss into and out of the associated foramina and soft tissues around the spine as you move in order to maintain their tonus and their glide.

You can see, this becomes a critical junction. There is some argument in physiology about what is normal for the L5-S1 relationship. Does L5 stay with the sacrum or does it go counter to it? My observations are that most of the time, it goes counter. When the right leg is load-bearing, the sacrum sidebends left, and by virtue of being sidebent, it also rotates right on the diagonal axis a little bit. As that sacrum is slightly right rotated as a part of being left sidebent, what is happening at L5? It’s either right-rotated with the sacrum, or it’s counter-rotating under the load from above. This pretty much depends on the postural habits, the amplitude of the lumbar lordosis, and the profile shape of the sacrum of the person in question.

If your client is someone who has fairly high amplitude spinal curves, then L5 is rotating away from the sacrum. If you’ve got somebody who’s a relatively low lordosis lumbar profile, flat sacrum in profile, and not much depth to the lumbar curve, then L5 goes with the sacrum. This is a variant that is determined by preexisting patterning of the postural qualities of every individual. There is some argument about these topics, and the answer is dependent on the body that you are looking at. The point of these fine distinctions is to be able to discern if the lumbosacral junction is normal or stressed, which is part of an evaluation for function. These distinctions are academic, until the person is in trouble, and then it matters when restoring normal motion.

Figure 10: When a person has a fixed right transitional diagonal axis, their sacrum will be right sidebent while standing equally on two feet. When palpating their sacral base, the left side will be inferior to the right, and deeper in the body.

For the sacrum, your primary therapeutic effectiveness will rest on understanding the horizontal-to-diagonal axes transitions. These transitory diagonal axes are a beautiful system. But, let’s imagine that you misstep off a curb, and come down with a straight right leg, your knee doesn’t absorb some of this load like usual, and you get a jolt. The sacrum can be suddenly taken into the load-bearing sidebend left, away from that load-bearing leg, and there can be a slight shearing load on the sacroiliac joint from the atypical impact. Then when you resume walking, when loadbearing on the left leg, the sacrum can’t sidebend right as it had a moment before the misstep. This event created a fixed diagonal axis (see Figure 10) and compromises the joint between L5 and the sacral base. This situation equals trouble and potentially the genesis of disk involvement as a consequence.

A fixed diagonal axis is a motion restriction of normal movement in which the ability of the sacrum to have the two alternating transitional axes during walking yields to having a single fixed diagonal axis on one side that doesn’t change when walking. This is so subtle and so universal that I will go so far as to say that most people who have chronic lumbosacral disc problems have a fixed sacral motion axis hiding below. In this condition, the sacral base is no longer horizontal in neutral, leaving L5-S1 to take the heat, and I do mean inflammation.  

When the sacral base of a person standing in neutral has a sidebend either right or left, L5 is always the first adaptation to the load. Let’s consider this case of a person with a fixed left sacral sidebend, in other words, a fixed right diagonal axis, and a fairly pronounced lumbar lordosis (where their vertebral curve is fairly deep). The sacrum will have a slight right rotation, conjunct with the right transitory diagonal axis. Their L5 will most likely be rotated left, counter to the sacrum. When they step on their right leg, the sacrum left sidebends as normal. But as they step on the left leg, the sacrum can’t sidebend away from the load, it can’t access the left transitory diagonal axis, and the person won’t be able to shift their thorax as far over the left leg as usual. This also inhibits normal motion at the lumbosacral junction.

Watching that person walk away from you, you can see their hips swing right as the sacrum sidebends left, but not able to swing left as far since now the sacrum cannot sidebend on to the right with a left diagonal axis. This motion restriction of the sacrum stresses the L5-S1 junction and starts to demand an adaptation to L4 articulations because half the time, they’re normal, and half the time they’re inhibited. This is the root of back pain for many people. When a person has low back pain absent blunt trauma, and absent hard falls, this could be the root of accumulated strain where a fixed diagonal axis gets established. The body can accommodate small motion restrictions by limiting lateral translation movements in walking. Over time these restrictions can take their toll and become symptomatic.  

Figure 11: Ligaments of a male pelvis with the anterosuperior view above and posterior view below. Copyright Thieme Medical Publishers Incorporated, 2023.

The main thing is that the fixed diagonal axis is a motion restriction of normal movement. It’s lawful in that sense. As the sacrum is sidebent left, the lumbar rotates right, yet if you have a fixed diagonal axis, there may also be a fixed right-rotated lumbar hiding directly above it. When they step on the other leg, the lumbar vertebrae can’t rotate the other way, it can’t participate in bringing the thorax over the left load-bearing leg. You will see people have a characteristic sidebend, this is a spontaneous antalgic gesture to avoid pain, and it is our primary diagnostic for a diagonal axis fixation. You will see these people come into your office saying, “My back is out.” You will see them in the street and just know what kind of pain that person is walking with. This particular pain pattern is the bane of a biped.

LAH: This makes me think about how a person might notice the asymmetry in their upper body, one shoulder higher than the other, but the origin story of that side-to-side difference is at the sacral base.

JS: The shoulders are a place where asymmetry often shows up. Usually, one shoulder is higher, and/or the clavicles are not horizontal. Fundamentally that asymmetry is either in the habitual use of the arms or in the underlying structures. There is the armature (framework) of the ribcage under them and that is sidebent left or right, and the shoulder girdle organization reflects it. Some people drive themselves crazy over an unsymmetrical shoulder girdle, not coming to terms with the sacrum having an underlying diagonal axis fixation.

Tactically, this applies directly to our ideal of balance as a series of horizontals around a central vertical axis of spatial organization. As we come to have a better understanding of the dynamics of the sacrum and the general spatial organization, our therapeutic success in establishing a vertical line for their whole body is going to improve.  

LAH: How else do you deduce the sacral action of an individual client?

JS: If I ask someone to just stand in front of me and I see the shoulder girdles lacking horizontal, classical clavicles – and of course, there is a lot of room for variation on this idea. If the client is a baker or a machinist, they are using their dexterity a certain way, you may have asymmetrical patterns at the girdle. The next inquiry is to ask them to sit on a bench and have them forward bend, is the thoracic spine in the middle? If yes, then the 'high shoulder' problem is in the shoulder girdle. If not, the problem is in the spine and rib cage. That’s a quick triage and not the whole story.

LAH: The hard part is both detecting what is happening and then choosing what to do about it.

JS: Well, there is a lot to say about the soft tissues around these bony structures, as we are talking about this one bony landmark, the sacrum, and its basic physiological and biomechanical axes. When things go wrong, you can identify the strain and movement restrictions by the bony landmarks, as they are embedded in the surrounding soft tissues. This includes, but is not limited to, the ligament beds, muscular attachments, pelvic floor, plus sacrotuberous and sacrospinous ligaments, which are extensions of the hamstrings (see Figure 11).

On the ventral side of the sacrum, you have the iliacus, which, incidentally, has big attachments on the anterior base of the sacrum (Siccardi, Tariq, and Valle 2022). If you have a sidebent sacrum, very often, you have iliacus involvement. The iliopsoas has a medial branch that comes out of the same attachment as the iliacus on the lesser trochanter of the femur. The psoas crosses over the pubic ramus, but goes up the lateral aspect of the lumbar vertebrae, to interact with the crura of the diaphragm at the ventral thoracolumbar junction (see Figure 12).

Figure 12: Anterior muscles of the hip and thigh of the right side (Removed: Rectus femoris, vastus lateralis, vastus medialis, iliopsoas, and tensor fasciae latae). Sacral base clearly visible. Copyright Thieme Medical Publishers Incorporated, 2023.

Sometimes, to affect that configuration of strain at L5-S1, we need to address the psoas to release the muscular component of that fixation. When the psoas concentrically contracts, it rotates the lumbar vertebrae away from the side of the contraction. Keeping that in mind, in the lumbar spine, the vertebrae rotate away from sidebending pressure. If you can figure out what the lumbar spine is doing in relation to that sacral sidebend, then you work with the psoas to affect the tone, which can help to restore adaptive mobility. In a sense, we help to uncouple the motion-restricted pattern of the sacrum, the sidebending, and rotation of the lumbar vertebrae, by working with psoas and iliacus tone.

The piriformis goes from the greater trochanter through the sciatic notch to the ventral surface of the sacrum. In sacral sidebend strain patterns, the piriformis is
in the party. While it is beyond the scope of this article to fully explain each of these sacral influences – you can teach this to yourself. It is a matter of being able to make sequential deductions like a detective. As body-oriented therapists, we each have to learn the palette of structures impacting the organization of the sacrum, be they biomechanical or physiological.

Having said that, one of the reasons we bother to learn these bony biomechanical patterns is because they are the basis of highly effective position/release techniques (Chaitow 2016). Let’s go back to our example: the fixation of the left sidebent sacrum, which (usually) is accompanied by a lumbar left rotation/right sidebend. This sets up a corresponding left sidebend thoracic spine, to bring the upper body above the right leg. The sacrum is sidebending away from that right load-bearing leg.

If I’m going to try and make a correction at that sacrum, then I’ll put that person on a bench and ask them to sidebend at the lumbar spine, a little to the right – working into the pattern (see Figure 13). That puts pressure on the lumbar spine to start turning further left, into the way that it is already under strain. At that moment, the pattern begins to 'unlatch' as the body goes a little bit deeper into the strain pattern. This is a classic indirect technique in which the body is brought to a position that slightly increases the strain, but also unlocks it a little bit. As soon as it unlocks, the components will begin to go into what’s called an induced motility response. This is characteristic of almost all indirect techniques. It feels like an unorganized motility, but the body can use the moment to restore normal motion.

Figure 13: For a fixed right transitional diagonal axis, have the client sit on a bench and ask them to sidebend right with their lumbar spine. This begins to work the pattern. When inviting the client to also move into spinal extension, keep anterior pressure on the sacral base, to create the opportunity of the fixation unlatching.

The sacral base can be treated in a similar way. If the sacrum is stuck sidebent left, then the sacral base is deep on the left side, around a right fixed diagonal axis. Remember that it will continue the physiological primary-respiratory-mechanism-movement around that diagonal axis. The physiology is working, and the position isn’t. With that in mind and from a seated position, sidebend the upper body left, to match the sacral strain. Then add some back and forward bending. Remember that the sacrum forward bends when the whole spine is back-bent. Setups of these positions – sidebending into the pattern, then adding forward and then back bending – are interventions to be done in small increments. In this way, the sacrum can be rocked in one of these directions while your thumbs 'listen' on the (more posterior) upper end of the right diagonal axis at the sacral base. When a neutral point is detected, then pin it, and ask them to come back to the midline. In this way, you can carry the sacrum back to its neutral, horizontal axis. This is one example from a whole body of position/release technique based on the understanding of normal motion in the region.  

LAH: You are really putting it all together – all the elements you’ve spoken of so far. It is an intervention with all those bits of information playing a role. I like how you’re bringing it back to the practitioner anchoring their contact to the posterior sacral base.  

JS: Right. And remember that if you back bend the whole spine, the sacral base goes bilaterally deep. So, start at neutral, put your contact point on either side of the midline at the posterior sacral base, at the fixed diagonal axis. Paying attention to the superior corner that is fixed, ask the client to back bend. That motion will sometimes unlock the fixed right axis as the person's back bend evokes it to move deep, as in an unrestricted back bend. It’s like a magic key.

Most fixed diagonal axis strains have a component at the inferior lateral angle of the sacrum as well. If the fixed axis is on the right side of the sacrum, then the left inferior lateral angle will have a corresponding motion restriction. A forward bend will address the inferior lateral angle that is correspondingly restricted. You can place your contact at the inferior lateral angle, and pin it like a fulcrum, and when you have them forward bend, the deep corner of the left sacral base can pop out.  In this example, you have inhibited the restriction and asked for normal movement. It is just basic position/release techniques to release a stuck diagonal axis with the sacrum.

Once the diagonal axis is released, the sacral horizontal axis of normal craniosacral rhythm movement is re-established. Then, by supporting the client’s natural physiological movement at the sacrum while supine, you can begin to make corrections in their lumbar spine. Attempting to de-stress the lumbar will have limited use to the long-term comfort of the client if the sacral base remains in a fixed diagonal axis.  

LAH: You mentioned another common strain pattern, the shearing strain at the sacroiliac joint. How is this different?

JS: What I’ve been describing so far, the horizontal axis and transitional diagonal axes of the sacrum, are a part of normal movement. When a sacrum is stuck on its diagonal axis, it is a restriction of normal motion. If we can put a positional load on it, as described, that asks it to move toward its neutral – bingo – sacrum usually comes home.

If you have a sacral strain pattern where the ilium has become shifted on the sacral joint and is locked on it, that’s a shearing strain. Most shears have the sacrum inferior on the ilium, and/or ilium superior on the sacrum. Shearing strains are non-physiological patterns. They never happen in ordinary movements. Shearing strains are usually associated with real trauma, deceleration injuries, where the leg gets jammed, a car accident, or the knee gets hit and drives the ilium superior and posterior – shearing the sacroiliac joint. Sometimes people will have a shear strain if they fall hard and a bit sideways, as if they missed the chair when going to sit down and landed on the floor on their ischial tuberosity.

Sacrum shearing is very painful, it is often hard to walk with this injury, and people will say they can’t weight-bear on that leg. With severe shearing strain, some people can’t walk at all. How do you diagnose a shear strain in the sacroiliac joint? Either the ilium is displaced superiorly, much greater than normal motion restriction, or when you palpate the sacrum and you find it is more inferior at the ilia than what you expect. The inferior lateral angle on the side of the down shear will be more prominent posteriorly than in an ordinary diagonal axis strain. People will point to the sacroiliac joint area and say it hurts there, or with a less acute shear, they will be functional but have performance pain during their sport. Those are signs of a shear strain.

LAH: I had this happen to me when I was pregnant. I was about thirty-six weeks pregnant, right at the end of the pregnancy, and when that relaxin hormone was naturally released, the ligaments of my body were looser than usual. I picked up my foot to tie my shoelace while standing on one foot, and I felt my sacrum slip dramatically inferior compared to my ilium. It was so immediately painful, and it was one of those personal moments where I was glad to be a Rolfer. Right then and there, I got onto the floor, and with movement and breathing, I got it to slip right back home. The shock of the injury stayed with me for a few days, but I was able to resolve it right away. It was a big lesson to me about what our clients go through; they experience these things, and then they don’t know what to do. The pain stays with them, gets stuck in their system, and then they come to see us.

JS: Perfect example. The world is full of people who have sacral shears. And if they don’t get treated, then the bigger structures, the muscles, begin to contract around it. Over time, you get changes in muscle tone and functional atrophy. The work of walking after that kind of injury is done by one side of the pelvis, the other side can’t complete the sequential steps of walking. The more time the person has this injury in their body, the bigger the discrepancy in tones from side to side. Often, we have to do general decompression and big muscle work distally as a preparatory input for our client’s system, to build the tonus so they can get into a position for the position/release technique to stabilize.

LAH: Do you have closing thoughts for our focus on the sacrum?

JS: Related to the sacrum, another set of important observations includes noting how the pelvic floor and the legs come together. Essentially, the legs belong on the outside of the ilia, with the exception of the piriformis, obturator internus, and iliopsoas, being trans-pelvic musculofascial structures. As soon as you go inside the pubic rami, then you’re metaphorically looking straight up at the pubococcygeus, which is the primary soft-tissue basket for the suspension of the lower pelvis and it metaphorically serves to keep your stuffings in place. The real work of the classic Rolfing Recipe's 'Fourth Hour' is to give the leg a greater range of extension. It works by releasing the abductors from either the quadriceps or hamstrings. Once we make that definition, people’s pelvic floors function with less interference from gross leg movements.  

Also, no discussion of the sacrum would be complete without talking about the coccyx. We can think of the coccyx as the rudder of the pelvic floor. If the coccyx is true in the midline, then your pubococcygeus can – other things being equal – do its suspensory job of also keeping your stuffings in. But the sacrum and coccyx are vulnerable to all the same injuries that we just talked about. Social trauma, impact trauma, horses, bicycles, and anything you straddle can damage the coccyx or displace the coccyx. The coccyx to the sacrum is a very particular joint, and literally, the coccyx can wag; it’s made so it’s got that kind of mobility.

As practitioners, we can work with our client seated and slide our fingers between the gluteal muscles and hook the tip of the coccyx, you can immediately feel whether it’s in the midline or not. It’s very responsive to indirect techniques. There is a simple technique that I learned from Rolfing SI Instructor Christoph Sommer, I don’t know where he got it. I have used it thirty to forty times to straighten sidebent coccyges. Medical practitioners sometimes go intra-anal or intravaginal to reach in and apply force to direct it home. This is outside the scope of practice for Rolfers and structural integration practitioners.

LAH: External coccyx work and movement invitations can be a great help in that territory. Thank you for this chat; it’s a reminder to keep sacral techniques fresh.

JS: All right, there we go. You are welcome.

Jan H. Sultan’s initial encounter with Dr. Rolf was in 1967 as her client. In 1969 he trained under her. In 1975, after assisting several classes, Rolf invited him to become an instructor. After further apprenticeship, she invited him to take on the Advanced Training. Over the next ten years, Sultan taught several Advanced Trainings with Peter Melchior, Emmett Hutchins, Michael Salveson, and other faculty members, collaborating on refinements to the Advanced Training. Sultan currently teaches Basic Trainings, continuing education, and Advanced Trainings for the Dr. Ida Rolf Institute and continuing education to the extended SI community. He feels strongly that his responsibility as an instructor goes beyond simply passing on what he was taught, but also includes the development of the ideas and methodology taught by Rolf.

Lina Amy Hack, BS, BA, SEP, became a Rolfer® in 2004 and is now a Certified Advanced Rolfer (2016) practicing in Canada. She has an honors biochemistry degree from Simon Fraser University (2000) and a high-honors psychology degree from the University of Saskatchewan (2013), as well as a Somatic Experiencing® Practitioner (2015) certification. Hack is the Editor-in-Chief of Structure, Function, Integration.


Barral, Jean-Pierre, and Alain Croibier. 2009. Manual therapy for the cranial nerves. London,UK: Churchill Livingstone.

Bordoni, Bruno, Stevan Walkowski, Bruno Ducous, and Filippo Tobbi. 2020. The cranial bowl in the new millennium and Sutherland’s legacy for osteopathic medicine: Part 1. Cureus 12(9):e10410.

Chaitow, Leon. 2016. Positional release techniques. Edinburgh, UK: Elsevier.

Di Terlizzi, Roberta, and Simon Platt. 2006. The function, composition and analysis of cerebrospinal fluid in companion animals: Part I – function and composition. Veterinary Journal 172(3):422-431.

Gracovetsky, Serge. 1988. The spinal engine. New York, NY: Springer-Verlag.

Hladky, Stephen B. and Margery A. Barrand. 2014. Mechanisms of fluid movement into, through and out of the brain: Evaluation of the evidence. Fluid and Barriers of the CNS 11(26).

Killer, Hanspeter E. 2013. Production and circulation of cerebrospinal fluid with respect to the subarachnoid space of the optic nerve. Journal of Glaucoma 22Suppl 5:S8-S10.

Ma, Qiaoli, Yann Decker, Andreas Müller, Benjamin V. Ineichen, and Steven T. Proulx. 2019. Clearance of cerebrospinal fluid from the sacral spine through lymphatic vessels. Journal of Experimental Medicine 216(11):2492-2502.

Mitchell, Fred L. and P. Kai Galen Mitchell. 1995. Normal coupled motions in the sacroiliac joints: Torsion and Unilateral sacral flexion. In The muscle energy manual, 33-40. East Lansing, Michigan: Met Press.

Nastoulis, E. M.-V. Karaksi, P. Pavlidis, V. Thomaidis, and A. Fiska. 2019. Anatomy and clinical significance of sacral variations: A systematic review. Folia Morphology 78(4):651-667.

Rasmussen, Thomas Rosenkilde, and Karl Christian Meulengracht. 2021. Direct measurement of the rhythmic motions of the human head identifies a third rhythm. Journal of Bodywork and Movement Therapies 26:24-29.

Siccardi M. A. , M. A. Tariq, and C. Valle. 2022. Anatomy, Bony Pelvis and Lower Limb, Psoas Major. [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from:

Sutherland, W. G., A. S. Sutherland, A. L. Wales, and Sutherland Cranial Teaching Foundation Inc. 1998. Contributions of thought: The collected writings of William Garner Sutherland, DO: Pertaining to the art and science of osteopathy including the cranial concept in osteopathy covering the years 1914-1954. Indianapolis, IN: Sutherland Cranial Teaching Foundation.

Sutherland, William G. 1939. The cranial bowl. Unknown location: Unknown publisher.

Upledger, John E. and Jon D. Vredevoogd. 1983. Craniosacral therapy. Seattle, WA: Eastland Press.

Fan Weeren, Rene. 2012. “Biomechanics of the pelvis.” Available from

Verbruggen, Stefaan W. and Niamh C. Nowlan. 2017. Ontogeny of the human pelvis. The Anatomical Record 300:643-653.


sacrum; embryology; spine; coccyx; ilia; innominate; ischium; pubis; acetabulum; legs; femur; pelvis; skull; craniosacral system; locomotion; walking; sacral shape; cerebrospinal fluid; CSF; primary respiratory mechanism; fixed diagonal axis; back pain. ■

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