Topics

Topic

design image
Long plantar ligament

The long plantar ligament is a strong and broad fibrous band situated on the plantar aspect of the foot. It is the longest ligament of the sole and plays a crucial role in maintaining the lateral longitudinal arch of the foot and stabilizing the calcaneocuboid joint.

It forms a fibrous tunnel for the tendon of the peroneus longus, converting a groove on the cuboid bone into a canal. The ligament is essential for maintaining foot stability, load transmission, and dynamic support during walking and running.

Injury or degeneration of the long plantar ligament contributes to flatfoot deformity, arch collapse, and chronic plantar pain.

Synonyms

  • Long calcaneocuboid ligament

  • Superficial plantar calcaneocuboid ligament

Origin, Course, and Insertion

  • Origin: Plantar surface of the calcaneus, anterior to the medial and lateral processes of its tuberosity

  • Course: Passes forward along the plantar aspect of the foot, superficial to the short plantar (plantar calcaneocuboid) ligament

  • Insertion:

    • Superficial fibers: attach to the bases of the 2nd to 5th metatarsals

    • Deep fibers: attach to the cuboid bone, forming the fibro-osseous tunnel for the tendon of peroneus longus

Relations

  • Superiorly: Short plantar ligament and tendon of peroneus longus (within its tunnel)

  • Inferiorly: Plantar aponeurosis and subcutaneous tissue

  • Medially: Plantar calcaneonavicular (spring) ligament

  • Laterally: Lateral plantar vessels and nerves, calcaneocuboid joint capsule

Nerve Supply

  • Lateral plantar nerve (a branch of the tibial nerve) provides sensory and proprioceptive innervation to the ligament and adjacent structures

Function

  • Arch support: Primary static stabilizer of the lateral longitudinal arch

  • Joint stability: Reinforces the calcaneocuboid joint, preventing midfoot collapse

  • Dynamic support: Assists peroneus longus in maintaining foot eversion and arch integrity

  • Load transmission: Distributes weight-bearing forces across the plantar aspect of the foot during gait

Clinical Significance

  • Sprains and strains: Common in athletes and dancers; result from overuse or forced plantar flexion

  • Degeneration: Chronic overload or aging leads to ligament laxity, contributing to flatfoot deformity

  • Rupture: Rare, but can occur with severe trauma or dislocation of the calcaneocuboid joint

  • Plantar fasciitis differentiation: Pain from long plantar ligament pathology can mimic plantar fasciitis but is typically more lateral

  • Imaging role: MRI is preferred for evaluating partial tears, degeneration, and inflammation; CT is helpful in assessing bone alignment or calcification

MRI Appearance

  • T1-weighted images:

    • Normal ligament: low signal intensity (dark), forming a continuous band from calcaneus to cuboid/metatarsal bases

    • Partial tear or degeneration: intermediate signal or thickening with indistinct margins

    • Complete tear: discontinuity or focal fluid gap replacing the ligament

  • T2-weighted images:

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

    • Pathology: bright hyperintense signal in partial or complete tear; surrounding soft-tissue edema visible

    • Degenerative changes appear as irregular or frayed signal at the calcaneal or cuboid attachment

  • STIR (Short Tau Inversion Recovery):

    • Normal: low signal

    • Pathologic ligament: bright hyperintense signal indicating edema, strain, or inflammation

    • Best sequence for detecting acute injury or periligamentous fluid

  • Proton Density Fat-Saturated (PD FS):

    • Normal ligament: thin, low-signal linear structure

    • Partial tear: focal bright linear signal within the ligament substance

    • Complete rupture: discontinuity with surrounding bright signal of fluid and edema

    • Chronic thickening or fibrosis shows intermediate heterogeneous signal

  • T1 Fat-Sat Post-Contrast:

    • Normal ligament: minimal or no enhancement

    • Inflammation or scar tissue: enhancing thickened ligament

    • Helps differentiate active inflammatory change from chronic degeneration

CT Appearance

Non-Contrast CT:

  • Ligament appears as a thin soft-tissue density band along the plantar surface of calcaneus and cuboid

  • Indirect signs of pathology include calcification, thickening, or irregularity at attachment sites

  • Bony abnormalities such as calcaneocuboid subluxation or cuboid sclerosis may be secondary findings

Post-Contrast CT (standard):

  • Ligament itself shows minimal enhancement

  • Adjacent soft tissue enhancement may indicate inflammation or scarring

  • Useful for evaluating calcaneocuboid alignment, bone fragments, or post-traumatic changes

MRI images

Long plantar ligament axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

Long plantar ligament axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI images

Long plantar ligament axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002

MRI images

Long plantar ligament axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00003

MRI images

Long plantar ligament sag cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

Long plantar ligament sagittal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000