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The Pelvic Girdle

Functions of the Pelvis
Joint Structure of the Pelvis
Kinematics of the Pelvis
Muscles at the Pelvis
Pelvis Stability
Mechanism of Injury at the Pelvis

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Objectives¡G After studying this topic, the students will be able to

  1. to identify the structure of the pelvis, including joint type, articular shape, and the surrounding tissues
  2. to describe joint motions occurring at the pelvis, including osteokinematic and arthrokinematic movements, muscle actions, and factors checking pelvic motions
  3. to understand the pelvic stability and the possible mechanisms of injury
  4. to explain the relationship of the muscle balance in the pelvis to the erect posture

  1. Neumann DA (2002).  Axial Skeleton¡G Osteology and Arthrology.  In Neumann DA: Kinesiology of the Musculoskeletal System: Foundations for Physical Rehabilitation. Philadelphia: Mosby.  Chapter 9, pp. 303-308.
  2. Smith LK, Weiss EL, Don Lehmkuhl L (1996). Brunnstrom's Clinical Kinesiology, 5th ed.  Philadelphia, F.A. Davis.  Chapter 8, pp. 266-300.

Functions of the Pelvis

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  • to link the lower extremity with the trunk
  • to transmit the load of the trunk to the lower extremity
  • to absorb the shock from the ground
  • to protect the internal organ
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    Joint Structure of the Pelvis

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    Joints at the Pelvis

  • sacroiliac joint (SI joint)
  • pubis symphysis (pubic joint)
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    Sacroiliac Joint (SI Joint)

  • proximal component¡G sacrum
  • irregular articular surface
  • distal component¡G innominate
  • irregular auricular surface of the ilium
  • joint type¡G uneven articular surface
  • no muscles cross over this joint
  • motions
  • sacral flexion
  • sacral extension
  • sacral forward torsion
  • Joint Structure of the Pelvis
    Kinematics of the Pelvis

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    Pubic Symphysis (Pubic Joint)

  • amphiarthrosis (fibrocartilage joint)¡G articular surfaces covered with hyaline cartilage and held togehter by an interpubic disc and ligaments
  • joint type¡G plane joint
  • motions
  • superior/ inferior glide
  • separation/ compression
  • functions
  • shock absorption during walking
  • for woman's baby delivery
  • Joint Structure of the Pelvis

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    Sacral Angle

  • the angle of the superior margin of the sacrum from the horizontal plane
  • healthy adults¡G ~30º
  • lumbar lordosis increased if the pelvis is anteriorly tilted.
  • spondylolithesis
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    Neutral position of the pelvis

  • the plane where both anterior superior iliac spines (ASIS) and the pubis symphysis are located is parallel to the frontal plane
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    Kinematics of the Pelvis

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    Sacral Flexion/ Extension

  • synonym¡G
    sacral flexion = sacral nutation
    sacral extension = sacral counter-nutation
  • joint involved¡G sacroiliac joint
  • plane of motion¡G sagittal plane
  • axis of rotation¡G a frontal axis passing through S2
  • motions¡G
  • sacral flexion¡G sacral promontory tilts anteriorly and inferiorly
  • sacral extension¡G sacral promontory back to the neutral position from an anterior-tilted position
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    Sacral Forward/ Backward Torsion

  • joint involved¡G sacroiliac joint
  • plane of motion¡G triplanar motion
  • axis of rotation¡G left and right diagonal axis
  • osteokinematic movements
  • right forward torsion on right diagonal axis (R on R)
  • left forward torsion on left diagonal axis (L on L)
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    Pelvic Motions

  • open kinematic chain motions
  • anterior tilt¡G ASIS moves anteriorly and inferiorly
  • posterior tilt¡G ASIS moves posteriorly and superiorly
  • lateral tilt to the left/right¡G one ASIS is higher than the other
  • rotation to the left/right¡G one ASIS anterior to the other
  • pelvic motions at stance (closed kinematic chain motions)

    Pelvic Motions Spinal Motions Hip Motions
    anterior tilt hyperextension slight flexion
    posterior tilt flexion extension
    lateral tilt to the left lateral flexion to the right right hip¡G slight adduction
    left hip¡G slight abduction
    left rotation without turning the trunk or moving the feet right rotation right hip¡G slight external rotation
    left hip¡G slight internal rotation
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  • pelvic motions 2º to trunk motions

    Trunk Motions Pelvic Motions
    flexion posterior tilt
    extension anterior tilt
    lateral flexion to the left lateral tilt to the left
    left rotation left rotation

  • pelvic motions 2º to hip motions

    Hip Motions Pelvic Motions
    bilateral hip flexion posterior tilt
    bilateral hip extension anterior tilt
    one hip flexion with the other hip extension forward leg side¡G posterior tilt and outward rotation
    backward leg side¡G anterior tilt and inward rotation
    one hip abduction abducted leg side¡G lifting
    adducted leg side¡G lower
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    Muscles Around the Pelvis

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    Muscles for Pelvic Anterior Tilt

  • hip flexors
  • iliopsoas
  • rectus femoris
  • lumbar extensors
  • erector spinae
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    Muscles for Pelvic Posterior Tilt

  • abdominal muscles
  • rectus abdominis
  • hip extensors
  • hamstrings
  • gluteus maximus
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    Muscles for Pelvic Lateral Tilt

  • muscles for lateral tilt to the right
  • left quadratus lumborum
  • right hip abductors
  • muscles for lateral tilt to the left
  • right quadratus lumborum
  • left hip abductors
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    Muscles for Pelvic Rotation

  • muscles for right rotation
  • left lumbar rotators
  • left hip external rotators
  • right hip internal rotators
  • muscles for left rotation
  • right lumbar rotators
  • right hip external rotators
  • left hip internal rotators
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    Pelvis Stability

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    Factors Affecting Sagittal Plane Stability of the Pelvis

  • bony configuration
  • trabecular system of the pelvis follows the weight-bearing line
  • tension of ligaments or other connective tissues
  • iliolumbar ligament
  • sacrospinous ligament
  • sacrotuberous ligament
  • sacroiliac ligament¡G anterior, posterior, and interosseous
  • dynamic stability of muscles
  • stretch-weakness vs. adaptive shortness (Kendall, 1969)
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    Factors Affecting Frontal Plane Stability of the Pelvis

  • dynamic stability of muscles
  • stretch-weakness vs. adaptive shortness (Kendall, 1969)
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    Mechanism of Injury at the Pelvis

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    Malalignment

  • leg length discrepancy
  • long leg side
  • hip adduction
  • elevated iliac crest
  • sidebending of lumbar spine to the same side
  • compensatory scoliosis at thoracic and cervical regions
  • short leg side
  • hip abduction
  • pelvis lateral tilt to the same side
  • sidebending of lumbar spine to the opposite side
  • compensatory scoliosis at thoracic and cervical regions
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    Established on 12/11/2002 and Last Updated 12/31/2004 © 2004 Huei-Ming Chai, PhD PT          All Right Reserved