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Ulnocarpal ligaments

The ulnocarpal ligaments are a group of strong connective tissue bands that stabilize the ulnar side of the wrist, connecting the ulna to the carpal bones. They are integral components of the ulnocarpal complex and function in conjunction with the triangular fibrocartilage complex (TFCC) to maintain wrist stability, particularly during ulnar deviation and pronation-supination.

They are divided into two main sets based on their orientation and location: the palmar (volar) and dorsal ulnocarpal ligaments. These ligaments reinforce the joint capsule and provide mechanical support between the distal ulna, lunate, triquetrum, and proximal carpal row.

Synonyms

  • Ulnocarpal ligament complex

  • Ulnar wrist capsular ligaments

  • Palmar and dorsal radiocarpal-ulnar bands

Location and Components

The ulnocarpal ligament complex is located on the ulnar aspect of the wrist, extending from the ulnar styloid process and ulnar capsule to the lunate and triquetrum bones. It is closely associated with the TFCC, often blending with its fibers.

Palmar (volar) ulnocarpal ligaments

  • Ulnolunate ligament: Extends from the base of the ulnar styloid and TFCC to the palmar aspect of the lunate.

  • Ulnotriquetral ligament: Extends from the ulnar capsule and TFCC to the palmar surface of the triquetrum.

  • Ulnocapitate ligament (variable): Runs obliquely from the ulna toward the capitate, occasionally blending with other palmar ligaments.

Dorsal ulnocarpal ligament

  • Extends from the dorsal capsule near the ulnar styloid to the dorsal aspects of the lunate and triquetrum.

  • Reinforces the posterior portion of the TFCC and limits excessive palmar flexion and ulnar translation of the carpus.

Relations

  • Anteriorly: Palmar radiocarpal ligaments, flexor carpi ulnaris tendon, and ulnar nerve within Guyon’s canal

  • Posteriorly: Extensor carpi ulnaris tendon and dorsal capsule

  • Laterally: Triangular fibrocartilage complex (TFCC) and distal radioulnar joint

  • Medially: Ulnar styloid process and ulnar head

Attachments

  • Proximal attachments: Base of the ulnar styloid process, ulnar capsule, and distal ulna near the fovea.

  • Distal attachments: Palmar and dorsal surfaces of the lunate, triquetrum, and occasionally the capitate.

  • Capsular integration: Continuous with the wrist joint capsule and TFCC, forming a strong ulnar stabilizing complex.

Function

  • Wrist stability: Prevents excessive ulnar deviation and dorsal translation of the carpus.

  • Load transmission: Transfers axial and shear forces from the carpus to the ulna through the TFCC.

  • Rotational control: Maintains alignment during pronation and supination of the forearm.

  • Shock absorption: Distributes stress between the ulnar head and proximal carpal bones during gripping and weight-bearing.

Clinical Significance

  • Injury mechanism: Commonly injured during fall on outstretched hand (FOOSH), forced ulnar deviation, or twisting trauma.

  • Associated pathologies:

    • TFCC tears (most common association)

    • Ulnar impaction syndrome

    • Ulnocarpal abutment or synovitis

    • Lunotriquetral instability

  • Symptoms: Ulnar-sided wrist pain, clicking, instability, reduced grip strength.

  • Imaging role: MRI and arthrography are gold standards for detecting partial or complete tears, fibrosis, or degeneration.

MRI Appearance

  • T1-weighted images:

    • Ligaments: Low signal (dark linear bands) extending from ulna to lunate/triquetrum.

    • Surrounding fat planes: Bright, aiding ligament visualization.

    • Tears: appear as interruption or discontinuity of low-signal fibers, sometimes with intermediate signal gap.

  • T2-weighted images:

    • Ligaments: Low signal due to dense collagen composition.

    • Pathology: Bright signal (hyperintensity) within or around ligament indicating edema or partial tear.

    • TFCC or ulnolunate interface: may show fluid signal extending through tear.

  • STIR:

    • Normal ligament: Dark to intermediate signal.

    • Partial tear or inflammation: Bright hyperintense signal at attachment sites.

    • Surrounding soft-tissue edema becomes hyperintense, highlighting injury.

  • Proton Density Fat-Saturated (PD FS):

    • Normal ligaments: Dark, well-defined linear bands.

    • Partial tear: focal bright signal within ligament substance.

    • Complete tear: gap filled with joint fluid or granulation tissue.

    • Degenerative change: irregular thickened appearance with mixed signal.

  • T1 Fat-Sat Post-Contrast:

    • Normal ligaments: Minimal or no enhancement.

    • Inflamed tissue or synovitis: Enhancement around ulnocarpal recess.

    • Chronic tear: peripheral enhancement outlining nonviable ligament fibers.

CT Appearance

Non-Contrast CT:

  • Ligaments: Not directly visualized; appear as thin low-density structures if surrounded by fat.

  • Useful for detecting associated bone abnormalities, such as ulnar styloid fractures, subchondral cysts, or osteophytes.

  • Ulnar variance and degenerative changes can be assessed precisely.

Post-Contrast CT (standard):

  • Ligament margins enhanced indirectly through capsular or synovial enhancement.

  • Helpful in evaluating chronic ulnar-sided wrist pain and adjacent synovitis.

MRI Arthrography Appearance

  • Direct arthrography enhances visualization of the ulnocarpal ligaments and TFCC.

  • Normal: Contrast remains confined to ulnocarpal recess without crossing ligament fibers.

  • Partial tear: Contrast tracks along ligament fibers but does not completely traverse.

  • Complete tear: Contrast freely passes between ulnocarpal recess and midcarpal joint.

  • Associated TFCC tear: Contrast extension into distal radioulnar joint or lunotriquetral recess.

CT Arthrography Appearance

  • Normal: Ligaments appear as fine linear low-attenuation bands bordered by contrast in the ulnocarpal recess.

  • Partial tear: Contrast insinuates between split or thinned ligament fibers.

  • Complete tear: Direct communication between ulnocarpal and radiocarpal compartments.

  • Chronic injury: Irregular thickening or calcific streaks along ligament course.

  • Excellent for evaluating ulnocarpal impaction, degenerative changes, and post-surgical integrity of ulnar wrist stabilizers.

MRI image

Ulnocarpal ligaments dorsal mri image

MRI image

Ulnocarpal ligaments palmar