OMM Review — Sacrum and Innominates
Original OMM review notes for sacral and innominate mechanics, torsions, and common diagnostic tests.
Sacral Axes and Motion
The sacrum moves around oblique axes (left and right) for torsional motion and a transverse axis for nutation/counternutation. Naming sacral torsion requires stating the side of rotation and the side of the oblique axis (e.g., left-on-right).
Sacral flexion = nutation (sacral base moves anterior/inferior). Sacral extension = counternutation (sacral base moves posterior/superior).
| Motion | Axis | Clinical note |
|---|---|---|
| Torsion | Oblique | Named by side of rotation on axis |
| Nutation | Transverse | Base anterior, apex posterior |
| Counternutation | Transverse | Base posterior, apex anterior |
| Rotation | Vertical | Whole sacrum rotates left/right |
Innominate Dysfunctions
The innominate can rotate anteriorly or posteriorly around the pubic symphysis, flare medially/laterally at the ASIS, or shear superiorly/inferiorly. Palpate ASIS, PSIS, ischial tuberosity, and pubic tubercle to compare sides.
| Dysfunction | Landmark findings |
|---|---|
| Anterior rotation | ASIS low, PSIS high, ischium high |
| Posterior rotation | ASIS high, PSIS low, ischium low |
| Inflare | ASIS medial |
| Outflare | ASIS lateral |
| Upslip/downslip | Iliac crest discrepancy with seated flexion |
Key Diagnostic Tests
The standing flexion test identifies a sacroiliac dysfunction: the side that moves first or more is the dysfunctional side. The seated flexion test removes lower-extremity influence; a positive seated test confirms an innominate or sacral origin.
A positive stork (Gillette) test suggests sacroiliac dysfunction on the weight-bearing side.
Common Pelvic Findings
- Pubic dysfunction: ASIS/PSIS may be symmetric, but pubic tubercles are not level.
- Sacral shear: one sacral sulcus is deeper due to superior/inferior glide.
- L5 commonly rotates opposite the sacrum in oblique-axis torsions.
Q: A patient has a deep right sacral sulcus and the sacrum rotates left on a right oblique axis. What is the somatic dysfunction?
A: Left-on-right sacral torsion. The sacrum rotates left, and the axis is right oblique.
Q: Seated flexion test is positive on the right and standing flexion is positive on the right. What does this suggest?
A: The dysfunction is more likely sacral or SI, not solely lower-extremity driven.