Pelvis

Centrilization of pelvis

Downward from spine as weight, divided into 2 parts by SI joint until acetabulum.

Upward force from the floor/lower limb, divided into 2 by SI joint and pubic symphysis

Anterior tilting of sacrum

Larger curves formed in spine

Posterior tilting of sacrum

Smaller curves in spine

Direct static stabilizers

Between joint surfaces, small and strong

• Lig. Sacroiliaca interossea

• Lig. Sacroiliaca anteriora

• Lig. Sacroiliaca posteriora

Indirect static stabilizers

Long, loose, weak, connects between lumbar spine and hip.

• Lig. iliolumbale

• Lig. Sacrotuberale

• Lig. Sacrospinale

Lig. Sacrotuberale

Controls/limits anterior tilting of sacrum (nutation)

Iliac bundle of Lig. iliolumbale

Weak during extension

Sacral bundle of Lig. Iliolumbale

Activated during extension.

Anterior sliding of L5 is controlled by this fiber.

Nutation in open kinematic chain

Mobility of iliac bone, proximal sacrum is fixed

Distal segment is pelvis, hence moveable, pelvis has posterior tilting.

Nutation in closed kinematic chain

Mobility of sacrum, distal iliac bone is fixed.

Proximal segment is movable (sacrum), sacrum has anterior tilting.

Counternutation in open kinematic chain

Mobility of iliac bone, sacrum is fixed.

Pelvis movable at a distal segment, pelvis tilted anteriorly.

Counternutation in closed kinematic chain

Mobility of sacrum, iliac bone is fixed

Pelvis is fixed, sacrum movable. Apex moves anteriorly inferiorly.

Dynamic stabilizers of pubic symphysis

• M. adductor longus → pulls symphysis to its side inferiorly.

• M. Rectus abdominis → Pulls superiorly.

• M. obliquus abdominis internus → Opposite to adductor longus. Forces are equal.

• M. Transverse abdominis → Stabilizer, protector of pelvic complex. In direct connection w/ thoracolumbar fascia and indirectly w/ deep lumbar extensors (multifidus).

Static stabilization of pelvis in sagittal plane

• Abdominal muscles

• Paravertebral muscles

• Quadratus lumborum

• Iliopsoas

• Gluteus maximus

Static stabilization of pelvis in frontal plane

Standing in both lower limbs → crossed synergism of ab-adductors.

Standing on one leg → Gluteus Medius.