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Quadrate ligament

The quadrate ligament, also known as the ligament of Denucé, is a small but functionally important fibrous structure located in the proximal radioulnar joint of the elbow. It extends between the radial notch of the ulna and the neck of the radius, reinforcing the inferior margin of the annular ligament and stabilizing the proximal radius during rotation.

This ligament plays a crucial role in limiting excessive supination and pronation, maintaining joint congruency, and guiding the radial head’s rotational movement within the annular ligament. It provides a proprioceptive and stabilizing function that complements the annular and interosseous membranes.

Synonyms

  • Ligament of Denucé

  • Quadrate ligament of the proximal radioulnar joint

  • Inferior radioulnar ligament (historical term)

Location and Attachments

  • Proximal attachment: Inferior margin of the radial notch of the ulna (below the annular ligament)

  • Distal attachment: Medial surface of the neck of the radius

  • Shape: Square or rectangular band, approximately 1 cm in height and 3–5 mm thick

  • Orientation: Fibers run horizontally between the ulna and radius, deep to the annular ligament

Relations

  • Anteriorly: Synovial membrane of the proximal radioulnar joint

  • Posteriorly: Joint capsule and radial neck

  • Superiorly: Annular ligament of the radius

  • Inferiorly: Upper portion of the interosseous membrane

  • Medially: Radial notch of the ulna

  • Laterally: Neck of the radius

Function

  • Stabilization: Restrains excessive radial rotation at the proximal radioulnar joint

  • Limitation of motion: Restricts supination beyond 160° and pronation beyond 70°

  • Reinforcement: Strengthens the inferior border of the annular ligament

  • Proprioception: Contains mechanoreceptors aiding in joint position sense

  • Load transmission: Contributes to distributing rotational stress between radius and ulna

Clinical Significance

  • Injury: May be stretched or torn in rotational forearm trauma or elbow dislocations

  • Instability: Laxity contributes to proximal radioulnar instability or chronic supination weakness

  • Post-traumatic fibrosis: May limit pronation-supination range

  • Surgical relevance: Identified and preserved in annular ligament reconstruction or radial head replacement procedures

  • Imaging role: Assessed for tears, scarring, or impingement in chronic elbow pain or restricted rotation

MRI Appearance

T1-weighted images:

  • Normal ligament: low signal (dark) linear band between radial neck and ulnar notch

  • Surrounding fat planes: bright, allowing contrast with the ligament

  • Adjacent cortical bone: low signal

  • Partial tear: focal thinning or discontinuity with intermediate signal

  • Chronic fibrosis: low-to-intermediate signal thickening

T2-weighted images:

  • Normal: dark (low signal), sharply marginated structure

  • Acute injury: bright or intermediate signal representing edema or partial tear

  • Post-traumatic scarring: irregular low-signal thickened band

  • Surrounding joint effusion or synovial fluid: bright hyperintensity outlining the ligament

STIR:

  • Normal ligament: dark linear band

  • Pathologic changes (edema, inflammation): bright hyperintense signal

  • Excellent for identifying acute ligament sprain or reactive changes in adjacent soft tissues

Proton Density Fat-Saturated (PD FS):

  • Normal ligament: uniformly dark, sharply defined

  • Partial tear or scarring: focal bright signal within or around ligament

  • Best sequence for evaluating ligament integrity and subtle fiber disruption

T1 Fat-Sat Post-Contrast:

  • Normal ligament: minimal enhancement

  • Inflamed or fibrotic ligament: patchy or peripheral enhancement

  • Surrounding synovial inflammation: enhancing soft tissue, helping differentiate ligament pathology from joint effusion

MRI Arthrogram Appearance

  • Joint capsule and annular ligament fill with injected intra-articular contrast

  • Quadrate ligament seen as a dark band bridging the ulna and radius, outlined by bright contrast in the joint recesses

  • Tears or laxity: Contrast may leak inferiorly between radius and ulna, indicating ligamentous incompetence

  • Enhances visualization of proximal radioulnar joint morphology, synovitis, or capsular thickening

CT Appearance

Non-Contrast CT:

  • Ligament itself not distinctly visualized due to soft-tissue density

  • Adjacent osseous landmarks (radial neck and ulnar notch) clearly seen

  • Helpful for detecting associated cortical irregularities, fractures, or calcifications near attachment sites

Post-Contrast CT (standard):

  • Ligament appears as a fine soft-tissue structure between ulna and radius

  • Enhancing synovial recesses highlight its course indirectly

  • Acute trauma: May show soft-tissue thickening or adjacent fluid attenuation

  • Chronic injury: Ossification or calcific deposits may be visible near attachment points

CT Arthrogram Appearance

  • Contrast outlines the proximal radioulnar joint recesses, clearly defining the quadrate ligament

  • Ligament appears as a non-opacified linear structure between the ulna and radius, bordered by bright contrast

  • Tears or laxity: Contrast tracks inferiorly between radius and ulna

  • Post-traumatic or degenerative change: Seen as irregularity or thickening along its course

  • Valuable in differentiating ligamentous injury from capsular or annular ligament pathology

MRI image

Quadrate ligament (ligament of Denucé) of elbow transverse bundle axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000

MRI image

Quadrate ligament (ligament of Denucé) of elbow transverse bundle axial cross sectional anatomy 3T MRI AI enhanced radiology image -img-00000-00000_00001