Pelvic Motion and Listings

Sacroiliac Joints and Pelvis

  • Understanding Sacroiliac Joints

  • Composed of Iliac Bone(s), Coccyx, Sacrum.

Kinematics of Sacroiliac Joint Motion

  • Key Movements

  • Total motion of SI joint is minimal.

  • Anterior Rotation (Extension): Ilum rotates towards sacrum.

  • Posterior Rotation (Flexion): Ilium rotates away from sacrum.

  • Described by full femoro-acetabular flexion/extension.

  • Hip Movements Impact SI Joint:

    • Hip Extension → Anterior rotation of Ilium.

    • Hip Flexion → Posterior rotation of Ilium.

Motion Nomenclature

  • Definitions

  • Left SI Flexion: Posterior rotation of left ilium.

  • Right SI Extension: Anterior rotation of right ilium.

Reference Points for Static Concepts

  • Posterior Superior Iliac Spine (PSIS)

  • Important landmark for pelvic listings.

  • Listing Definitions:

    • AS (Anterior Superior): Fixed in Flexion.

    • PI (Posterior Inferior): Fixed in Extension.

Detail on Static and Dynamic Listings

  • If ilium lacks anterior rotation → Extension restriction (flexion misalignment). PI Ilium

  • Conversely, if it lacks posterior rotation → Flexion restriction (extension misalignment). AS Ilium

Sacral Kinematics

  • Nutation: Sacral base moves anterior/inferior.

  • Counter-Nutation: Sacral base moves posterior/superior.

  • Associated movements affect trunk and SI joint mechanics during posture changes.

  • Key Terms:

  • AI (Anterior Inferior): Sacrum fixed in nutation.

  • PS (Posterior Superior): Sacrum fixed in counternutation.

Movement Relations

  • Anterior sacral movement (nutation) → Posterior ilium rotation (SI Flexion).

  • Posterior sacral movement (counter-nutation) → Anterior ilium rotation (SI Extension).

Additional Movements at the SI Joint

  • Gait Dynamics:

  • SI Joint and pelvic motion influence gait.

  • Includes internal/external rotation of SI joints and oblique axis movements.

  1. PSIS moves towards midline = internal rotation. When

not moving you have an internal rotation restriction. In

static terminology it is said to be “stuck” in external

rotation and is referred to as an

EX ilium.

  1. PSIS moves away from the midline = external rotation.

Any lack of motion in this direction is called an external

rotation restriction. In static terminology it is said to be

“stuck” in internal rotation and is referred to as an IN

ilium.

Oblique Axes Dynamics

  • Left Oblique Axis & Right Oblique Axis: Important for understanding rotational dynamics during movement.

  • Movements contribute to gyroscopic stability during locomotion.

Summary of Sacroiliac Motion and Statics

  • Static vs. Motion Listings:

  • Motion terminology correlates with action; static listings always indicate a restricted motion.

Conclusion

  • Key to managing and understanding pelvic health is an understanding of SI joint movements, terminology, and associated malpositions.