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Volar ulnolunate ligament

The volar ulnolunate ligament is a strong intrinsic component of the ulnocarpal complex of the wrist. It extends from the anterior (volar) margin of the ulnar head and triangular fibrocartilage complex (TFCC) to the volar surface of the lunate bone, forming an important stabilizing connection between the distal ulna and the proximal carpal row.

This ligament acts in concert with the ulnotriquetral ligament and ulnocapitate ligament to maintain ulnocarpal joint stability and distribute load between the ulna and carpus during wrist motion. It plays a crucial role in stabilizing the lunate, particularly during pronation and supination movements of the forearm.

Synonyms

  • Palmar ulnolunate ligament

  • Volar radiocarpal ulnolunate ligament (component of ulnocarpal complex)

Origin, Course, and Insertion

  • Origin: Volar aspect of the ulnar head and the palmar portion of the triangular fibrocartilage complex (TFCC)

  • Course: Runs obliquely distally and laterally across the ulnocarpal joint space on the volar aspect of the wrist

  • Insertion: Volar surface of the lunate bone, near its ulnar margin, blending with the capsule of the radiocarpal joint

Relations

  • Anteriorly: Flexor tendons of the wrist, particularly the flexor carpi ulnaris and flexor digitorum profundus

  • Posteriorly: Ulnocarpal joint capsule and lunate bone

  • Medially: Ulnotriquetral ligament and TFCC components

  • Laterally: Radiolunate ligament and capsule of the radiocarpal joint

Attachments

  • Proximal attachment: Ulnar head and anterior TFCC margin

  • Distal attachment: Volar surface of the lunate bone

  • Capsular integration: Merges with the anterior joint capsule, reinforcing the volar aspect of the wrist joint

Nerve Supply

  • Articular branches from the anterior interosseous nerve and ulnar nerve (via deep palmar branches)

Function

  • Joint stabilization: Prevents excessive volar translation of the lunate and limits abnormal ulnar deviation

  • Load transmission: Helps transmit compressive forces between the ulna and proximal carpal row

  • Coordination: Works synergistically with the ulnotriquetral and radiolunate ligaments for ulnocarpal stability

  • Dynamic support: Maintains lunate alignment during pronation, supination, and wrist flexion-extension

Clinical Significance

  • Ligament tears: May occur in conjunction with TFCC injuries or ulnocarpal impaction syndrome

  • Degenerative changes: Chronic overload can cause fraying or attenuation seen in wrist arthritis

  • Instability: Partial or complete tear can contribute to lunate instability and ulnocarpal pain

  • Trauma association: Commonly injured in forced ulnar deviation, hyperextension, or fall on outstretched hand (FOOSH)

  • Imaging role: MRI and arthrography are key for evaluating integrity, fiber continuity, and associated TFCC or carpal pathology

MRI Appearance

  • T1-weighted images:

    • Normal ligament: low signal (dark band) between the ulnar head and lunate

    • Adjacent fat planes: bright, providing contrast to ligament

    • Tear or degeneration: focal discontinuity, irregularity, or mild intermediate signal replacing normal dark band

  • T2-weighted images:

    • Normal ligament: dark, thin continuous band

    • Partial tear: focal hyperintense signal within the ligament substance or at attachment sites

    • Complete tear: discontinuity with fluid-bright gap between ulnar head and lunate

    • Periligamentous edema or joint effusion: hyperintense surrounding signal

  • STIR:

    • Normal ligament: dark to intermediate signal

    • Pathology: bright hyperintense signal around ligament margins (edema or synovitis)

    • Very sensitive for early inflammatory or post-traumatic changes

  • Proton Density Fat-Saturated (PD FS):

    • Normal: dark continuous band of uniform thickness

    • Partial tears: focal bright linear signal crossing fibers

    • Complete tears: absence or full-thickness bright gap

    • May show associated changes in TFCC or ulnotriquetral ligament

  • T1 Fat-Sat Post-Contrast:

    • Normal ligament: minimal or no enhancement

    • Inflammation or post-traumatic scarring: focal or diffuse enhancement around ligament

    • Chronic degeneration: may show peripheral rim enhancement

MRI Arthrography Appearance

  • Contrast fills the ulnocarpal joint and outlines the volar ulnolunate ligament distinctly

  • Partial tear: small amount of contrast insinuates into the ligament substance or attachment site

  • Complete tear: contrast traverses between the ulna and lunate through the disrupted fibers

  • Allows excellent evaluation of associated TFCC tears, ulnotriquetral injury, and synovitis

CT Appearance

Non-Contrast CT:

  • Ligament not directly visualized; seen as a fine soft-tissue density connecting ulna and lunate

  • Indirect findings: ulnocarpal joint effusion, small bony avulsions, or subchondral sclerosis in chronic cases

  • Useful for detecting ulnar impaction changes or lunate bone pathology

Post-Contrast CT (standard):

  • Enhances visualization of surrounding capsule and soft tissues

  • Inflammatory thickening or fibrotic changes may enhance subtly

CT Arthrography Appearance

  • Contrast outlines the ulnocarpal joint and the volar ulnolunate ligament

  • Partial tear: contrast tracks along ligament fibers but does not cross the full thickness

  • Complete tear: contrast passes freely between ulna and lunate, indicating full disruption

  • Excellent for assessing associated TFCC defects, ulnotriquetral communication, and lunate cartilage condition

  • High-resolution CT arthrography provides superior bone–ligament interface detail compared to MRI

MRI images

Volar ulnolunate ligament axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

Volar ulnolunate ligament coronal mri image

MRI images

Volar ulnolunate ligament mri sag image