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Calcaneocuboid ligament (Bifurcate ligament)

The calcaneocuboid ligament, also called the bifurcate ligament, is a strong Y-shaped ligament in the midfoot. It originates from the anterior process of the calcaneus and divides into two distinct bands: the calcaneocuboid ligament (lateral band) and the calcaneonavicular ligament (medial band). The lateral band attaches to the cuboid bone, forming the calcaneocuboid ligament proper.

This ligament is a key stabilizer of the midfoot, supporting the calcaneocuboid joint and resisting excessive inversion forces. It also functions as part of the bifurcate complex, which is frequently injured in inversion ankle sprains and midfoot trauma.

Synonyms

  • Bifurcate ligament (lateral band)

  • Dorsal calcaneocuboid ligament

  • Calcaneocuboid part of bifurcate ligament

Origin, Course, and Insertion

  • Origin: Anterior process of the calcaneus

  • Course: Runs obliquely forward and laterally from the calcaneus as one limb of the bifurcate ligament

  • Insertion: Dorsolateral surface of the cuboid bone

Tendon Attachments

  • Lies adjacent to the tendons of the extensor digitorum longus and peroneus tertius near the dorsolateral foot

  • Surrounded by retinacular fibers and dorsal foot fascia, helping stabilize the lateral tarsal region

Relations

  • Superiorly: Dorsum of the foot and extensor tendons

  • Inferiorly: Calcaneocuboid joint capsule and lateral aspect of plantar ligaments

  • Medially: Calcaneonavicular band of the bifurcate ligament

  • Laterally: Peroneus longus tendon crossing the cuboid groove

Function

  • Joint stability: Provides dorsal reinforcement to the calcaneocuboid joint

  • Resists inversion stress: Acts as a check ligament against excessive inversion and medial displacement

  • Part of midfoot stabilizers: Contributes to the structural integrity of the bifurcate ligament complex

  • Load distribution: Helps maintain alignment of the calcaneocuboid joint during gait and weight-bearing activities

Clinical Significance

  • Injury: Frequently torn in inversion ankle sprains (especially with bifurcate ligament complex injury)

  • Symptoms: Pain, swelling, and tenderness at the dorsolateral midfoot

  • Chronic instability: May lead to midfoot instability or calcaneocuboid joint degeneration

  • Imaging role: MRI and CT are crucial for detecting partial tears, avulsions, and associated fractures of the calcaneal anterior process

MRI Appearance

  • T1-weighted images:

    • Normal ligament: low signal (dark, cord-like band)

    • Partial tear: thickening and intermediate signal intensity

    • Complete tear: discontinuity with bright signal gap

    • Adjacent bone marrow edema may appear as intermediate-to-bright signal in calcaneus or cuboid

  • T2-weighted images:

    • Normal ligament: low-to-intermediate signal, slightly darker than T1

    • Partial tears: linear or focal hyperintense signals within ligament fibers

    • Complete tears: fluid-filled gap (bright signal) replacing ligament fibers

    • Surrounding edema and joint effusion appear bright

  • STIR (Short Tau Inversion Recovery):

    • Normal ligament: low signal band

    • Pathology: bright hyperintense signal in tears, avulsions, or adjacent edema

  • Proton Density Fat-Saturated (PD FS):

    • Normal ligament: uniform low signal

    • Tears: hyperintense clefts or irregular bright signals in ligament substance

    • Excellent for identifying subtle sprains and partial disruptions

  • T1 Fat-Sat Post-Contrast:

    • Normal: minimal or no enhancement

    • Pathology: enhancement of torn fibers, periligamentous tissue, or synovitis

    • Distinguishes postoperative scarring (enhancing) from residual intact ligament (non-enhancing)

CT Appearance

Non-Contrast CT:

  • Ligament itself not directly visualized (appears as a thin soft-tissue density band)

  • Indirect signs: small avulsion fragments at the calcaneal anterior process or cuboid attachment

  • Adjacent joint incongruity or calcification in chronic injuries

Post-Contrast CT (standard):

  • Ligament visualization limited

  • May show peri-ligamentous enhancement if inflammation or post-injury synovitis present

MRI image

Calcaneocuboid ligament (Bifurcate ligament) axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Calcaneocuboid ligament (Bifurcate ligament) coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000