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Anatomy of the Pelvic Girdle and Hip Joint

Overview of the Pelvic Bones

  • The pelvic girdle consists of bones that are involved in various functions, including muscle attachments and support for the body.

Key Pelvic Bones and Landmarks

  • Pubis Bone: Represents one-fifth of the pelvis.

    • Features notable landmarks important for muscle attachments.

  • Ilium: The uppermost part of the pelvis.

    • Iliac Crest: The ridge felt on the top of the hips; runs along the upper border of the ilium.

Anterior Landmarks of the Ilium

  • Anterior Superior Iliac Spine (ASIS):

    • The superior spine on the anterior side of the ilium.
    • Easily palpated; commonly noted in clinical and anatomical discussions.

  • Anterior Inferior Iliac Spine (AIIS):

    • Located just below the ASIS on the anterior side.
    • Important for muscle attachments.

Posterior Landmarks of the Ilium

  • Posterior Superior Iliac Spine (PSIS):

    • Located on the posterior side of the ilium; can be palpated.

  • Posterior Inferior Iliac Spine (PIIS):

    • Situated below the PSIS on the posterior side.

Ischium Bone

  • The ischium constitutes two-fifths of the pelvis.
  • Obturator Foramen: A large hole in the ischium, not primarily associated with human movement.
  • Ramus of the Ischium: An arch-like structure connecting the ischium to the pubis.
  • Ischial Tuberosity:
    • A bony prominence serving as the origin point for hamstrings.
    • Often described in terms of sensation when sitting on hard surfaces.

Pubis Bone Landmarks

  • Pubic Tubercle: A bump on the pubis bone.
  • Superior Pubic Ramus: An archway connecting to the ilium.

Sacrum and Coccyx

  • The Sacrum is formed from five fused vertebrae, connecting the left and right pelvic bones.
    • Base of the Sacrum: The superior part.
    • Apex of the Sacrum: The inferior part.
  • The Coccyx or tailbone, located at the base of the sacrum, is an important landmark for the conclusion of the vertebral column.

Joint Structures

  • Acetabulum: The socket for the hip joint created by contributions from the ilium, ischium, and pubis.
  • Sacroiliac Joint (SI Joint): The joint formed between the sacrum and ilium, allowing for limited motion and importance in stability.

Hip Joint

  • Hip Joint: A ball-and-socket joint formed between the head of the femur and the acetabulum.
    • Acetabular-femoral Joint: Another term for the hip joint, indicating its structure.

Important Ligaments of the Hip

  • Pubofemoral Ligament:

    • Connects the pubis to the femur; limits external rotation and hip extension.

  • Iliofemoral Ligament:

    • Large ligament connecting the ilium to the femur; assists in postural stability and limits excessive hip extension.

  • Ischiofemoral Ligament:

    • Connects the ischium to the femur; limits internal rotation and some adduction.

  • Superior and Inferior Pubic Ligaments:

    • Stabilize the pubic symphysis joint.

  • Transverse Acetabular Ligament:

    • Bridges the gap in the acetabulum, providing structural support.

  • Ligament of the Head of the Femur:

    • Attaches at the fovea capitis, anchoring the femur to the acetabulum.

Muscle Groups in the Pelvic Region

  • Iliacus Muscle: Originates at the iliac crest, merging with psoas muscles to form iliopsoas.

  • Psoas Major Muscle: Arises from T12 to L5 vertebrae, contributing to flexion at the hip joint.

  • Psoas Minor Muscle: Smaller muscle originating around T12 and L1.

  • Iliopsoas Muscle: ( ext{Common tendon formed by iliacus and psoas muscles to insert at the lesser trochanter of the femur.} )

  • Rectus Femoris Muscle: Originates from ASIS, acting as a hip flexor, and a part of the quadriceps group.

  • Sartorius Muscle:

    • Longest muscle in the body; spans from ASIS to tibia, aiding in hip and knee movements.