Pelvis, Sacrum & Innominate Kinematics

• Superior Transverse Axis (at S2 Level): Passes horizontally through the articular processes posterior to the sacral canal at the second sacral segment. Governs Respiratory and Craniosacral motion. During inhalation / cranial flexion, the sacral base moves posteriorly (counternutation / sacral extension). During exhalation / cranial extension, the sacral base moves anteriorly (nutation / sacral flexion).
• Middle Transverse Axis: Passes through the anterior convexity of the sacrum at S2. Governs Postural motion during forward and backward bending. Forward bending forces the sacral base anteriorly until the sacrotuberous ligaments tighten; backward bending forces the sacral base posteriorly.
• Inferior Transverse Axis (at S3/S4 Level): Passes through the inferior articular surface of the sacrum. Governs Dynamic Iliosacral motion (the innominates rotating anteriorly and posteriorly on the sacrum during walking).

Sacral torsions occur around two dynamic oblique axes named for the superior pole of origin:

• Right Oblique Axis: Originates at the superior margin of the right sacral base and extends diagonally across to the left Inferior Lateral Angle (ILA).
• Left Oblique Axis: Originates at the superior margin of the left sacral base and extends diagonally across to the right Inferior Lateral Angle (ILA).
• Physiological Locomotion: During normal ambulation, when weight is transferred onto the left leg, the sacrum rotates forward around the left oblique axis (Left-on-Left torsion). As the right leg swings forward and strikes the ground, weight shifts to the right oblique axis (Right-on-Right torsion).

The patient sits with feet flat on the floor (locking the innominates onto the ischial tuberosities to eliminate lower extremity hamstring/quadriceps bias) while the physician's thumbs palpate the bilateral PSISs. The patient bends forward:

Patient prone. The physician palpates the sacral sulci (medial to the PSIS) and the ILAs (lateral to the sacrococcygeal junction):

• Deep Sulcus: The sacral sulcus that sinks deeper anteriorly represents the sacral base that has rotated forward.
• Posterior / Inferior ILA: The ILA that is prominent posteriorly and pushed inferiorly indicates the dysfunctional sacral apex. In a sacral torsion, the deep sulcus and posterior ILA are on OPPOSITE sides.

This is the definitive test differentiating forward (physiological) from backward (non-physiological) torsions:

Sacral torsions are named in the format: [Direction of Sacral Rotation] on [Oblique Axis]:

• Left-on-Left (L/L): Positive seated flexion on Right ightarrow Left Axis. Deep sulcus on Right ightarrow Left rotation. Good spring ightarrow Forward Torsion: L/L.
• Right-on-Left (R/L): Positive seated flexion on Right ightarrow Left Axis. Deep sulcus on Left ightarrow Right rotation. Poor spring / hard stop ightarrow Backward Torsion: R/L.
• Right-on-Right (R/R): Positive seated flexion on Left ightarrow Right Axis. Deep sulcus on Left ightarrow Right rotation. Good spring ightarrow Forward Torsion: R/R.
• Left-on-Right (L/R): Positive seated flexion on Left ightarrow Right Axis. Deep sulcus on Right ightarrow Left rotation. Poor spring / hard stop ightarrow Backward Torsion: L/R.

Applying the three coupling axioms solves any L5-sacral vignette in under 10 seconds: (1) L5 Rotation and Sacral Rotation are ALWAYS OPPOSITE around a vertical axis (if L5 rotates right, the anterior surface of the sacrum rotates left); (2) L5 Sidebending and the Sacral Oblique Axis are ALWAYS on the SAME side (if L5 is sidebent left, the sacral torsion occurs around the left oblique axis); and (3) Flexion/Extension mechanics correspond (a neutral Type I L5 N SL RR couples with a forward sacral torsion L on L, whereas a non-neutral Type II flexed/extended L5 F RL SL couples with a backward sacral torsion R on L). Always verify whether the prompt asks for the L5 diagnosis or the sacral torsion diagnosis before selecting the answer choice.

• Anterior Innominate Rotation: The innominate rotates anteriorly and inferiorly around the inferior transverse sacral axis.
  • ASIS: Inferior and anterior on the affected side.
  • PSIS: Superior on the affected side.
  • Muscle Spasm: Associated with hypertonicity of the quadriceps / rectus femoris.
  • Leg Length: Functional long leg on the affected side.
• Posterior Innominate Rotation: The innominate rotates posteriorly and superiorly.
  • ASIS: Superior and posterior on the affected side.
  • PSIS: Inferior on the affected side.
  • Muscle Spasm: Associated with hypertonicity of the hamstrings.
  • Leg Length: Functional short leg on the affected side.

• Superior Innominate Shear (Upslip): The entire hemipelvis shifts cephalad. Both the ASIS and PSIS are SUPERIOR on the affected side, and the ipsilateral pubic tubercle is superior. Standing flexion test is positive on the affected side. Commonly caused by stepping into a hole, landing hard on an extended knee, or direct axial impact.
• Inferior Innominate Shear (Downslip): Both ASIS and PSIS are inferior; rare, typically seen following forceful traction injuries.
• Pubic Shears (Superior vs. Inferior): Evaluated at the pubic symphysis. Tender and asymmetrical pubic tubercles, frequently seen postpartum or following kicking/cutting athletic trauma.

• The Golden Sequence of Pelvic OMT: When multiple pelvic somatic dysfunctions exist, treat in the strict order: 1. Pubic Symphysis → 2. Innominates → 3. Sacrum → 4. Lumbar Spine (L5). Treating the pubic symphysis first unlocks the anterior pelvic ring and often resolves secondary innominate asymmetries.
• Superior vs. Inferior Pubic Shear: Diagnosed by palpating the superior surface of the pubic rami/tubercles and performing the Standing Flexion Test. A Right Superior Pubic Shear exhibits a positive right Standing Flexion Test and a superiorly displaced right pubic tubercle (tight rectus abdominis). Treated by hip extension with abduction/internal rotation off the side of the table (MET).
• Pubic Compression (Adduction) vs. Pubic Gapping (Abduction): Treated with the 'Shotgun' Technique: patient supine with hips and knees flexed; patient performs 3 isometric hip abduction contractions against physician's hands at the lateral knees (releases adductor spasm), followed by 3 isometric hip adduction squeezes against physician's interposed forearm/fist (resets the pubic fibrocartilaginous disc).

To treat a forward sacral torsion (L on L or R on R) using Muscle Energy Technique, the patient is placed in the lateral Sims position with the oblique axis side DOWN (for L on L, the patient lies on their left side and rotates the chest/anterior thorax prone onto the table, locking the lumbosacral junction in flexion and right rotation). The physician stands in front of the patient, monitors the sacral base/L5 junction with the cephalad hand, and flexes both hips and knees until motion is felt at the lumbosacral junction (stabilizing the left oblique axis). The physician then drops the patient's ankles off the side of the table toward the floor (inducing left lumbosacral sidebending to push the right sacral base posteriorly toward symmetry) and instructs the patient to push their ankles upward toward the ceiling against isometric resistance for 3 to 5 seconds, repeating 3 to 5 times.

To treat a backward sacral torsion (R on L or L on R) with MET, the patient lies in the lateral recumbent position with the oblique axis side DOWN (for R on L, left side down). Unlike forward torsions where the chest is prone, in a backward torsion the physician rotates the patient's upper trunk posteriorly into supine rotation (thoracolumbar extension), extends the bottom (left) leg on the table, and flexes the top (right) hip and knee until the L5-S1 segment is localized. The physician pushes the patient's top knee downward toward the floor to engage the rotational barrier while the patient pushes the top ankle/knee upward against isometric resistance during inhalation (since inhalation promotes sacral counseling/base posterior motion, assisting the patient effort).

In a unilateral sacral flexion (anterior/inferior sacral shear), one sacral base has sheared anteriorly and inferiorly without an oblique axis, producing a deep sacral sulcus and a posterior-inferior ILA on the same side, with a positive seated flexion test on that ipsilateral side. To treat a left unilateral sacral flexion, the patient lies prone in the Sphinx position (inducing physiological sacral flexion/nutation on the normal right side); the physician places the heel of the hand over the prominent left posterior-inferior ILA, applies an anterior-superior force during patient exhalation (when the sacral base moves posteriorly), and holds the sacral base posterior during subsequent inhalations for 3 to 5 respiratory cycles.

For an anterior innominate rotation (ASIS inferior, PSIS superior, ipsilateral functional long leg), the patient lies supine with the dysfunctional side near the edge of the table. The physician flexes the ipsilateral hip and knee until motion is felt at the sacroiliac joint—engaging the posterior rotational barrier via hamstring and gluteal tension—and instructs the patient to push the knee/hip into extension toward the floor against isometric resistance for 3 to 5 seconds before flexing further into the new barrier. Conversely, for a posterior innominate rotation (ASIS superior, PSIS inferior, ipsilateral functional short leg), the patient's dysfunctional leg is dropped off the side of the table into hip extension (stretching the rectus femoris and iliopsoas to pull the ASIS anteriorly and inferiorly into the barrier), and the patient contracts the hip flexors upward toward the ceiling against resistance.

A superior innominate shear (upslipped innominate)—caused by falling onto an outstretched leg or stepping unexpectedly into a hole, presenting with all four landmarks (ASIS, PSIS, pubic tubercle, and ischial tuberosity) shifted superiorly and an apparent short leg—is treated supine by abducting the leg 15 to 20 degrees (loose-packed sacroiliac position), slightly internally rotating the hip, and applying axial caudal traction through the ankle while the patient inhales deeply and coughs or exhales. Pubic symphysis shears are frequently released first using the 'pelvic shotgun' technique: with the patient supine and hips/knees flexed to 90 degrees, the patient performs three isometric hip abductions against the physician's hands, followed by three isometric hip adductions against the physician's forearm placed between the knees, often producing an audible articulatory pop as the pubic rami self-correct.

The piriformis muscle originates on the anterior surface of S2–S4, exits through the greater sciatic foramen superior to the sciatic nerve (or is pierced by the common fibular division in ~15% of individuals), and inserts on the superior border of the greater trochanter. When the hip is extended, the piriformis acts as an external rotator; however, when the hip is flexed beyond 60 to 90 degrees, its line of pull shifts anterior to the axis of rotation, converting it into an internal rotator and abductor. For Piriformis Counterstrain, the patient lies prone and the ipsilateral hip is flexed to 90–135 degrees with abduction and external/internal rotation fine-tuned (F ABD ER/IR). For Piriformis MET, the patient lies supine with the hip flexed to 90 degrees and adducted/internally rotated into the restrictive barrier while pushing the knee laterally into abduction/external rotation against isometric resistance.