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Posterior wall of acetabulum

The posterior wall of the acetabulum forms the posterolateral rim of the hip socket and is a major structural component of the acetabulum. It provides the posterior containment of the femoral head and contributes to hip joint stability during weight-bearing and rotational movements.

It is thicker than the anterior wall and curves upward from the ischium toward the superior acetabular region. The posterior wall also provides part of the attachment surface for the labrum, supporting congruity and distributing joint forces.

Synonyms

  • Posterior acetabular margin

  • Posterior acetabular rim

  • Posterior lip of acetabulum

Location and Structure

  • Position: Posterolateral aspect of the acetabulum, extending from the ischial body to the superior acetabulum.

  • Structure:

    • Forms the bony rim of the posterior acetabulum

    • Thick cortical bone, concave in shape

    • Provides attachment for the posterior labrum

  • Articular component: Contributes to the posterior portion of the lunate articular surface

Relations

  • Superiorly: Superior acetabular rim and ilium

  • Inferiorly: Ischial body and ischial tuberosity region

  • Anteriorly: Posterior column of the acetabulum

  • Posteriorly: Obturator internus tendon, ischiofemoral ligament, posterior hip capsule

  • Laterally: Gluteal muscles adjacent to the outer surface

  • Medially: The acetabular fossa and quadrilateral surface

Function

  • Provides posterior containment for the femoral head

  • Contributes to hip joint stabilization, especially during flexion and internal rotation

  • Supports and anchors the posterior acetabular labrum

  • Helps distribute load transmitted from the femoral head to the pelvis

  • Essential in controlling posterior hip translation

Clinical Significance

  • Posterior wall fractures: Common in dashboard injuries, often associated with posterior hip dislocations

  • Labral tears: Frequently involve the posterior labrum due to its load-bearing function

  • Femoroacetabular impingement: Posterior overcoverage or retroversion may contribute to impingement patterns

  • Surgical relevance: Key structure in acetabular fracture fixation and hip arthroscopy orientation

MRI Appearance

T1-weighted images:

  • Cortical bone: very low signal (black)

  • Marrow spaces within posterior acetabulum: bright due to fatty marrow

  • Labrum: low signal triangular structure attached to posterior rim

  • Excellent for defining anatomy and marrow composition

T2-weighted images:

  • Cortical bone: dark

  • Marrow: bright, slightly less than on T1

  • Articular cartilage: intermediate-to-bright signal

  • Posterior labrum: low signal; tears show altered morphology or bright signal clefts

  • Clear depiction of acetabular concavity and posterior rim contour

STIR:

  • Normal bone marrow: intermediate-to-dark

  • Provides strong fat suppression for contrast between bone, cartilage, and surrounding soft tissues

  • Useful for detecting edema in acute fractures or labral–capsular interface injuries (without describing pathology detail)

T1 Fat-Saturated Post-Contrast

  • Normal bone: mild uniform enhancement of marrow

  • Labrum and capsule: thin peripheral enhancement

  • Enhances visualization of cartilage surfaces, capsular insertions, and acetabular contour

  • Smooth enhancement pattern helps outline the posterior acetabular rim clearly

CT Appearance

Non-Contrast CT:

  • Cortical bone: very high attenuation, sharply defined

  • Posterior acetabular wall visualized as thick curved rim

  • Articular surface: smooth, concave lunate outline

  • Excellent for evaluating bony thickness, acetabular version, and rim geometry

MRI images

Posterior wall of acetabulum MRI axial image-img-00000-00000