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First plantar cuneometatarsal ligament (Plantar lisfranc ligament)

The first plantar cuneometatarsal ligament (also known as the plantar Lisfranc ligament) is a strong, thick fibrous band that forms part of the plantar tarsometatarsal (Lisfranc) ligament complex. It connects the plantar surface of the medial cuneiform to the plantar base of the second metatarsal, lying deep to the flexor tendons of the midfoot.

This ligament is the strongest stabilizer among the three Lisfranc ligament components (dorsal, interosseous, and plantar). It provides significant resistance to plantar and rotational displacement of the metatarsal bases and plays a vital role in maintaining the integrity of the medial longitudinal arch.

Synonyms

  • Plantar Lisfranc ligament

  • Plantar medial cuneiform–second metatarsal ligament

  • First plantar cuneometatarsal ligament (to 2nd metatarsal base)

Origin, Course, and Insertion

  • Origin: Plantar surface of the medial cuneiform near its anterior aspect

  • Course: Runs obliquely laterally and distally across the plantar aspect of the Lisfranc joint, deep to the plantar fascia and flexor tendons

  • Insertion: Plantar base of the second metatarsal

Relations

  • Superiorly: First tarsometatarsal joint capsule and interosseous Lisfranc ligament

  • Inferiorly: Plantar aponeurosis and deep plantar fascia

  • Medially: Medial cuneiform and attachments of plantar tarsometatarsal ligaments

  • Laterally: Base of the second metatarsal and the plantar surface of the second cuneometatarsal ligament

  • Anteriorly: Proximal shaft of the second metatarsal

  • Posteriorly: Plantar surface of the medial cuneiform

Function

  • Primary stabilizer: Strongly resists plantar and lateral displacement of the second metatarsal

  • Arch support: Maintains the medial longitudinal and transverse arches during stance and gait

  • Load distribution: Transfers weight-bearing forces from forefoot to midfoot

  • Joint integrity: Reinforces the Lisfranc joint complex in combination with interosseous and dorsal ligaments

  • Gait mechanics: Provides rigidity to the midfoot during push-off phase

Clinical Significance

  • Lisfranc complex injury: The plantar ligament is often disrupted along with the interosseous ligament in high-grade Lisfranc injuries

  • Mechanism: Usually due to axial load or twisting on a plantarflexed foot (e.g., sports trauma or fall from height)

  • Symptoms: Plantar midfoot pain, swelling, ecchymosis (especially plantar bruising), and difficulty weight-bearing

  • Consequences: Missed or untreated tears lead to chronic instability, medial arch collapse, and post-traumatic arthritis

  • Imaging role: MRI best visualizes the plantar ligament and its integrity; CT helps detect subtle avulsion fractures or diastasis

Nerve Supply

  • Supplied by articular branches of the medial plantar nerve and deep fibular (peroneal) nerve innervating the plantar tarsometatarsal joint region

MRI Appearance

  • T1-weighted:

    • Normal ligament: low-signal (dark), thick band extending from medial cuneiform to base of second metatarsal

    • Surrounded by bright subcutaneous and plantar fat, aiding contrast

    • Partial tear: irregularity, thickening, or discontinuity with intermediate signal

    • Complete tear: loss of continuous low-signal band, with small gap or retraction

  • T2-weighted:

    • Normal ligament: low signal intensity

    • Partial or full tear: bright hyperintense signal replacing ligament fibers

    • Adjacent bone marrow edema common at ligament insertion sites

    • May show fluid tracking along the plantar midfoot in acute sprain

  • STIR:

    • Normal: dark linear structure

    • Injured ligament: bright hyperintense periligamentous signal, with edema or hemorrhage in surrounding soft tissue

    • Useful for detecting subtle sprains not apparent on other sequences

  • Proton Density Fat-Saturated (PD FS):

    • Normal: thick, sharply defined dark band on coronal or oblique sagittal images

    • Partial tear: bright focal hyperintensity within ligament or at bony attachment

    • Complete rupture: discontinuity with fluid-filled gap between medial cuneiform and second metatarsal

    • Associated findings: plantar fascia thickening, joint effusion, bone marrow edema

  • T1 Fat-Sat Post-Contrast:

    • Normal ligament: minimal or no enhancement

    • Injured ligament: enhancement at tear margins due to hyperemia and granulation tissue

    • Chronic injuries may show subtle linear enhancement from fibrosis or scar formation

CT Appearance

Non-Contrast CT:

  • Ligament not directly visualized, but attachment sites on plantar medial cuneiform and base of 2nd metatarsal appear closely apposed

  • Indirect signs of injury:

    • Widening between medial cuneiform and 2nd metatarsal base (>2 mm)

    • Small plantar avulsion fragment (“fleck sign”) at 2nd MT base or cuneiform

    • Dorsal subluxation or malalignment of metatarsal base on sagittal reformation

  • Chronic injuries: sclerosis, cortical irregularity, or osteophyte formation at ligament insertions

Post-Contrast CT (standard):

  • Ligament remains indistinct, but periligamentous enhancement may indicate inflammation or healing

  • Excellent for assessing bony alignment, subtle avulsion fractures, and midfoot instability

MRI images

First plantar cuneometatarsal ligament (Plantar lisfranc ligament) axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

First plantar cuneometatarsal ligament (Plantar lisfranc ligament) coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001