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Lateral collateral ligament of big toe (lateral metatarsophalangeal collateral ligament)

The lateral collateral ligament (LCL) of the big toe, also known as the lateral metatarsophalangeal collateral ligament, is a strong fibrous band that reinforces the lateral aspect of the first metatarsophalangeal (MTP) joint. It connects the lateral side of the metatarsal head to the lateral base of the proximal phalanx of the hallux, providing stability, alignment, and resistance to varus stress during movement.

It is one of a pair of collateral ligaments — medial and lateral — that maintain the integrity of the MTP joint and work in coordination with the plantar plate, joint capsule, and sesamoid apparatus to ensure proper hallux mechanics during gait.

Synonyms

  • Lateral metatarsophalangeal collateral ligament

  • Lateral collateral ligament of the hallux

  • Lateral side ligament of first MTP joint

Location and Structure

  • The ligament extends obliquely downward and forward from the lateral tubercle of the first metatarsal head to the lateral base of the proximal phalanx.

  • It is composed of dense collagen fibers, forming part of the capsuloligamentous complex of the MTP joint.

  • The fibers blend distally with the plantar plate and lateral sesamoid complex, integrating into the joint capsule.

  • Its orientation allows it to resist lateral displacement and stabilize the joint during dorsiflexion and push-off.

Relations

  • Medially: Plantar plate and lateral sesamoid bone

  • Laterally: Joint capsule and pericapsular fat pad

  • Superiorly (dorsal): Extensor hallucis longus tendon

  • Inferiorly (plantar): Flexor hallucis brevis tendon and lateral sesamoid apparatus

  • Anteriorly: Base of proximal phalanx of hallux

  • Posteriorly: Head of the first metatarsal bone

Attachments

  • Proximal attachment: Lateral tubercle of the first metatarsal head

  • Distal attachment: Lateral surface of the base of the proximal phalanx of the great toe

  • Additional fibers: Merge with the plantar plate, joint capsule, and lateral sesamoid ligament complex

Nerve Supply

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

  • Sensory fibers contribute to proprioceptive feedback during toe motion

Function

  • Joint stabilization: Prevents varus (inward) deviation of the proximal phalanx at the first MTP joint

  • Support of plantar plate: Contributes to joint congruency and weight distribution during gait

  • Dynamic balance: Maintains lateral stability of the hallux during push-off and propulsion

  • Protection: Prevents excessive lateral rotation or subluxation of the MTP joint

Clinical Significance

  • Sprains and partial tears: Common in sports involving pivoting or forced lateral toe deviation (e.g., football, ballet)

  • Chronic instability: Repetitive strain or ligament laxity can lead to hallux varus deformity

  • Hallux valgus surgery: LCL is often imbalanced or stretched; its integrity is vital for correction

  • Sesamoid pathology: Lateral sesamoid subluxation or fracture can involve LCL disruption

  • Pain and swelling: Present along lateral aspect of first MTP joint after overuse or trauma

  • Imaging role: MRI is essential for diagnosing ligament tears, sprains, and pericapsular inflammation

MRI Appearance

  • T1-weighted images:

    • Ligament: Low signal (dark band) extending obliquely from metatarsal head to proximal phalanx

    • Adjacent bone marrow: Bright signal due to fatty marrow

    • Joint capsule: thin low-signal structure around MTP joint

    • Partial tears: focal thickening or discontinuity with mild intermediate signal

  • T2-weighted images:

    • Normal ligament: Low signal (dark) against intermediate cartilage background

    • Partial tears or sprains: bright hyperintense regions within ligament fibers

    • Joint fluid or edema: hyperintense, outlining ligament margins

    • Associated findings: periligamentous fluid, plantar plate thickening, or bone marrow edema at attachments

  • STIR:

    • Normal ligament: intermediate-to-dark signal intensity

    • Pathologic: bright hyperintensity from edema, partial tear, or inflammatory change

    • Useful for detecting early sprain or occult ligament injury

  • Proton Density Fat-Saturated (PD FS):

    • Normal ligament: intermediate-to-dark, sharply defined margins

    • Partial or complete tear: focal bright signal or discontinuity

    • Pericapsular inflammation: bright surrounding edema

    • Ideal for visualizing associated plantar plate injury or sesamoid complex involvement

  • T1 Fat-Sat Post-Contrast:

    • Normal ligament: minimal enhancement

    • Inflamed or torn fibers: focal or diffuse enhancement indicating hyperemia

    • Pericapsular enhancement: suggests synovitis or reactive capsulitis

    • Chronic scarring: peripheral enhancement with central low-signal fibrosis

CT Appearance

Non-Contrast CT:

  • Ligament: not directly visible but inferred from soft-tissue density lateral to MTP joint

  • Bony attachments: well-defined cortical margins at metatarsal head and proximal phalanx

  • Pathology:

    • Avulsion fractures at ligament insertions

    • Lateral sesamoid malalignment or subluxation

    • Degenerative osteophytes or joint-space narrowing in chronic instability

Post-Contrast CT (standard):

  • Ligament and capsule appear as thin enhancing soft-tissue bands

  • Enhancement of periligamentous tissues indicates inflammation or capsulitis

  • Excellent for evaluating bony avulsions, osteophytes, and sesamoid alignment abnormalities

MRI image

Lateral collateral ligament of big toe (lateral metatarsophalangeal collateral ligament) axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

lateral collateral ligament of big toe (lateral metatarsophalangeal collateral ligament) axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001