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Lateral collateral ligament of interphalangeal joint of foot

The lateral collateral ligament (LCL) of the interphalangeal (IP) joint of the foot is a fibrous band situated on the lateral side of each interphalangeal articulation. It connects the head of the proximal phalanx to the base of the adjacent distal phalanx, providing lateral stability and resisting varus stress during flexion and extension of the toes.

Each interphalangeal joint (both proximal and distal, in the lesser toes) has two collateral ligaments—medial and lateral—working together to maintain alignment of the phalanges and prevent side-to-side displacement. The great toe (hallux) has a single interphalangeal joint with its own robust medial and lateral collateral ligaments.

Synonyms

  • Lateral collateral ligament of the toe

  • Lateral phalangeal collateral ligament

  • Lateral capsular thickening of interphalangeal joint

Location and Structure

  • Position: Located laterally at each interphalangeal joint (proximal and distal) of the second to fifth toes, and the single IP joint of the hallux.

  • Shape: Short, strong, rounded cords of dense fibrous connective tissue.

  • Attachments:

    • Proximal attachment: Lateral tubercle of the head of the proximal (or middle) phalanx.

    • Distal attachment: Lateral margin of the base of the distal (or next) phalanx.

  • Fiber direction: Oblique, running from dorsal-proximal to plantar-distal, blending with the plantar plate and joint capsule.

  • Composition: Dense collagen bundles interwoven with fibrous tissue from the joint capsule and adjacent tendons.

Relations

  • Medially: Joint capsule and plantar plate

  • Laterally: Subcutaneous tissue and skin

  • Dorsally: Extensor tendons (extensor digitorum longus or extensor hallucis longus)

  • Plantar aspect: Flexor tendons (flexor digitorum longus or flexor hallucis longus)

  • Adjacent structures: Digital arteries, nerves, and small bursae near tendon sheaths

Nerve Supply

  • Digital branches of the medial and lateral plantar nerves (from tibial nerve)

  • Dorsal digital branches of the deep fibular nerve

Function

  • Joint stability: Prevents excessive varus deviation at the interphalangeal joint.

  • Guides motion: Maintains congruency during flexion and extension by tightening in extension and relaxing in flexion.

  • Load distribution: Transmits and balances stress between the phalanges during gait.

  • Support to capsule and plantar plate: Reinforces lateral joint capsule, working with plantar structures to resist multidirectional stress.

Clinical Significance

  • Sprain or rupture: Often results from toe hyperextension or lateral twisting injury (“turf toe” variant in great toe).

  • Chronic laxity: Leads to lateral deviation deformities or instability of the interphalangeal joint.

  • Arthritis: Degenerative changes can weaken ligament insertion, predisposing to instability.

  • Traumatic avulsion: Small bony fragment at the lateral base of distal phalanx may indicate collateral ligament avulsion.

  • Surgical relevance: Repair or reconstruction may be required after dislocations or chronic deformity correction.

  • Imaging importance: MRI is best for soft-tissue integrity; CT shows associated bony avulsions or degenerative change.

MRI Appearance

  • T1-weighted images:

    • Ligament: Low signal (dark linear band) along lateral joint margin.

    • Adjacent bone marrow: Bright fatty signal.

    • Cartilage: Intermediate-to-low signal overlying phalangeal heads.

    • Pathology: Partial tears or avulsions may show focal discontinuity or indistinct margins with adjacent intermediate signal.

  • T2-weighted images:

    • Ligament: Low-to-intermediate signal intensity, slightly darker than tendons.

    • Marrow: Bright signal.

    • Joint fluid: Bright hyperintensity outlining ligament margins.

    • Pathology: Bright hyperintense signal at ligament origin/insertion with periligamentous edema indicating sprain or partial tear.

  • STIR:

    • Normal ligament: Intermediate-to-dark signal.

    • Pathology: Bright hyperintense signal along lateral joint margin due to edema or acute injury.

    • Sensitive for ligament strain, soft-tissue swelling, and early inflammatory change.

  • Proton Density Fat-Saturated (PD FS):

    • Normal ligament: Intermediate-to-dark, thin continuous band.

    • Partial tear or strain: Focal bright signal at attachment sites or within fibers.

    • Periligamentous edema: Bright fluid signal extending into lateral capsule.

  • T1 Fat-Sat Post-Contrast:

    • Normal ligament: No significant enhancement.

    • Inflamed or healing ligament: Mild linear enhancement.

    • Chronic fibrosis: Minimal or patchy enhancement with surrounding soft-tissue thickening.

CT Appearance

Non-Contrast CT:

  • Ligament: Not directly visualized, but seen as soft-tissue thickening along lateral joint margin.

  • Bone attachments: Appear smooth; small avulsion fragments or cortical irregularities indicate injury.

  • Joint alignment: Easily assessed for subtle subluxation or malalignment due to ligament damage.

Post-Contrast CT (standard):

  • Enhanced capsule or soft tissue: Suggests inflammation, synovitis, or scarring near ligament.

  • Useful for: Detecting chronic changes, small avulsion fractures, and pericapsular fibrosis following trauma.

MRI image

Lateral collateral ligament of interphalangeal joint of foot coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Lateral collateral ligament of interphalangeal joint of foot coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI image

Lateral collateral ligament of interphalangeal joint of foot sag cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002