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Spring ligament complex

The spring ligament complex, also known as the plantar calcaneonavicular ligament, is a group of strong fibrocartilaginous ligaments located on the medial side of the foot. It extends from the sustentaculum tali of the calcaneus to the plantar surface of the navicular bone, providing essential support to the head of the talus and maintaining the integrity of the medial longitudinal arch.

It is not a single band but a complex of three ligamentous components:

  • Superomedial calcaneonavicular ligament (SMCNL) – the strongest and most clinically relevant portion, supporting the talar head.

  • Medioplantar oblique calcaneonavicular ligament (MPOCNL) – contributes to stability of the talonavicular joint.

  • Inferoplantar longitudinal calcaneonavicular ligament (IPLCNL) – lies most inferiorly, blending with fibers of the tibialis posterior tendon sheath.

Failure of the spring ligament complex is strongly associated with adult-acquired flatfoot deformity, often secondary to tibialis posterior tendon dysfunction.

Synonyms

  • Plantar calcaneonavicular ligament

  • Medial arch ligament

  • Talonavicular support ligament

Origin, Course, and Insertion

  • Origin: Sustentaculum tali of the calcaneus

  • Course: Fibrocartilaginous bands pass medially and anteriorly beneath the head of the talus

  • Insertion: Plantar and medial surfaces of the navicular bone, often blending with the tibialis posterior tendon and deltoid ligament fibers

Relations

  • Superiorly: Head of the talus

  • Inferiorly: Tibialis posterior tendon and navicular tuberosity

  • Medially: Deltoid ligament

  • Laterally: Talonavicular joint capsule

  • Anteriorly: Navicular bone and articular cartilage

  • Posteriorly: Sustentaculum tali of calcaneus

Function

  • Arch support: Maintains the medial longitudinal arch of the foot

  • Talar head support: Forms a sling beneath the talar head to prevent downward displacement

  • Joint stability: Stabilizes the calcaneonavicular and talonavicular articulations

  • Dynamic role: Works synergistically with tibialis posterior tendon and plantar fascia during gait

Clinical Significance

  • Degeneration or tear: Leads to talar head displacement, loss of medial arch, and adult-acquired flatfoot deformity

  • Posterior tibial tendon dysfunction: Often coexists with spring ligament pathology

  • Symptoms: Medial foot pain, arch collapse, valgus deformity, and difficulty in prolonged standing or walking

  • Imaging importance: MRI is crucial for evaluating spring ligament tears, degeneration, or insufficiency; CT assesses osseous alignment and secondary changes

MRI Appearance

  • T1-weighted images:

    • Normal: spring ligament appears as a low signal (dark), well-defined band beneath the talar head

    • Degeneration: ligament thickening with intermediate signal

    • Tears: focal discontinuity with bright signal at defect site

  • T2-weighted images:

    • Normal: low signal intensity (darker than on T1)

    • Pathology: bright hyperintense areas within ligament substance indicating edema, partial tears, or degeneration

    • Associated: talar head uncovering, joint effusion, and tibialis posterior tendon pathology

  • STIR:

    • Normal: uniformly dark band

    • Tears or degeneration: hyperintense signal in ligament and surrounding soft tissues

  • Proton Density Fat-Saturated (PD FS):

    • Normal: low-signal, compact ligament

    • Partial tear: linear bright signal within ligament substance

    • Complete tear: absence of intact fibers with fluid-filled gap beneath talar head

  • T1 Fat-Sat Post-Contrast:

    • Normal: minimal enhancement

    • Inflamed or torn ligament: patchy or diffuse enhancement, often extending to adjacent soft tissues

CT Appearance

Non-Contrast CT:

  • Normal: visualized as a thin soft-tissue band bridging calcaneus and navicular

  • Tears/degeneration: poorly defined, thickened, or absent ligament

  • Indirect signs: talar head subluxation, loss of arch height, degenerative changes in talonavicular joint

Post-Contrast CT:

  • Limited role for direct ligament evaluation

  • Adjacent inflammatory changes may enhance

  • CT primarily used to assess osseous alignment and secondary degenerative changes in flatfoot deformity

MRI images

spring ligament complex axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

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

MRI images

spring ligament complex sagittal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI images

spring ligament complex sagittal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI images

spring ligament complex sagittal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002