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Posterior glenoid labrum

The posterior glenoid labrum is the fibrocartilaginous rim located along the posterior margin of the glenoid cavity of the scapula. It deepens the glenoid fossa, stabilizing the humeral head and preventing posterior translation. It blends with the joint capsule and attaches to the posterior glenoid rim, forming a key structural component of the posterior shoulder stabilizing complex.

It serves as the attachment point for the posterior band of the inferior glenohumeral ligament, contributes to the posterior capsule, and supports the long head of the triceps origin in some individuals. Because the posterior shoulder experiences shear and compressive forces, the posterior labrum is a common site for posterior labral tears, internal impingement, and degenerative changes.

Synonyms

  • Posterior labrum

  • Posterior glenoid rim labrum

  • Posterior glenoid fibrocartilage

Location and Structure

  • Located along the posterior one-third of the glenoid rim

  • Composed of dense fibrocartilage with a triangular cross-section

  • Firmly attached to the bone at the chondrolabral junction

  • Contributes to the posterior glenoid concavity and enhances stability

  • Continuity with posterior capsule and posterior band of inferior glenohumeral ligament

Relations

  • Anteriorly: Glenoid cartilage and humeral head

  • Posteriorly: Joint capsule and infraspinatus tendon

  • Superiorly: Posterior superior labrum near the biceps anchor

  • Inferiorly: Posterior band of the inferior glenohumeral ligament

  • Laterally: Articular surface of humeral head

  • Medially: Posterior glenoid bone

Attachments

  • Fibrocartilage firmly anchored to posterior glenoid rim

  • Posterior capsule blends with posterior labrum

  • Attachment for posterior band of inferior glenohumeral ligament

  • Supports joint stability during posterior load

Function

  • Deepens the glenoid cavity, increasing joint stability

  • Prevents posterior humeral head translation

  • Helps distribute load across posterior glenoid rim

  • Provides attachment for stabilizing capsuloligamentous structures

  • Contributes to proprioception of the shoulder

Clinical Significance

  • Posterior labral tears: Seen in traumatic posterior dislocation, repetitive overhead motion, or internal impingement

  • Paralabral cysts: May form adjacent to labral tears and compress the suprascapular nerve

  • Glenoid dysplasia: May alter the morphology and thickness of posterior labrum

  • Imaging importance: Essential to evaluate tears, degeneration, posterior instability, and labral variants

  • Surgical relevance: Repair of posterior labrum crucial in athletes with posterior instability or internal impingement

MRI Appearance

T1-weighted images:

  • Labrum appears as a low-signal (dark) triangular structure at the posterior glenoid rim

  • Glenoid cartilage shows intermediate signal

  • Fat in the joint recess appears bright, outlining the labrum

T2-weighted images:

  • Normal posterior labrum: uniform low signal

  • Clear contrast with joint fluid (bright)

  • PD/T2 sequences highlight morphology of the chondrolabral junction

STIR:

  • Labrum remains dark due to dense fibrocartilage

  • Joint fluid and synovial recesses appear hyperintense

  • Highlights subtle surrounding edema in adjacent soft tissues

Proton Density Fat-Saturated (PD FS):

  • Ideal sequence for labral assessment

  • Normal labrum: dark, sharply marginated

  • Labral morphology and attachment clearly seen with fat suppression

  • Fluid appears bright, improving contrast between labrum and tears

CT Appearance

Non-Contrast CT:

  • Labrum has similar density to soft tissue; not directly well visualized

  • Glenoid rim bone morphology easily assessed

  • Useful for evaluating posterior glenoid bone loss or retroversion

Post-Contrast CT (Standard CT Arthrography):

  • Intra-articular contrast outlines the labrum

  • Normal posterior labrum appears as a smooth, uniform, triangular filling defect

  • Provides excellent visualization of chondrolabral junction and posterior recess

  • Enhances detection of small irregularities or detachment at the posterior rim

MRI image

Posterior glenoid labrum