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Quadratus plantae tendon

The quadratus plantae tendon is the distal continuation of the quadratus plantae muscle, located in the second layer of the sole of the foot. The muscle arises from the calcaneus and inserts via its tendon into the lateral border of the tendon of the flexor digitorum longus (FDL). Its action corrects the oblique pull of the FDL, assisting in flexion of the lateral four toes.

The tendon itself is short but clinically relevant because of its role in toe flexion mechanics, stabilization of the foot during gait, and compensatory function when other toe flexors are weak.

Synonyms

  • Flexor digitorum accessorius tendon

  • Tendon of quadratus plantae

  • Plantar accessory flexor tendon

Origin, Course, and Insertion

  • Origin: Medial and lateral surfaces of the calcaneus (via quadratus plantae muscle fibers)

  • Course: Short tendon extending from the muscle belly in the sole of the foot, coursing obliquely forward and medially

  • Insertion: Lateral border of the flexor digitorum longus tendon, joining its tendinous slips to assist toe flexion

Tendon Attachments

  • Joins the flexor digitorum longus tendon before it divides into four digital slips

  • Strengthens and redirects the pull of FDL tendons toward the axis of the foot

  • Sometimes provides accessory slips to the lateral toes

Relations

  • Superiorly: Tendons of the flexor digitorum longus

  • Inferiorly: Plantar aponeurosis and fatty tissue of the sole

  • Medially: Flexor hallucis longus tendon (with which it may share fibers via vincula)

  • Laterally: Abductor digiti minimi muscle

Function

  • Toe flexion assistance: Redirects FDL pull to produce straight flexion of the lateral four toes

  • Foot stabilization: Helps maintain plantar support during gait and standing

  • Synergist role: Works with flexor hallucis longus and flexor digitorum brevis in toe flexion

  • Biomechanics: Prevents medial deviation of toes by balancing FDL oblique pull

Clinical Significance

  • Injury: Rarely injured in isolation but may be affected in severe plantar trauma or lacerations

  • Tendinopathy: Can contribute to chronic plantar foot pain and dysfunction

  • Surgical relevance: Important in tendon transfer surgeries and plantar foot reconstructions

  • Imaging role: Evaluation of tendon integrity in cases of trauma, plantar fasciitis-like syndromes, or suspected tendon tears

MRI Appearance

  • T1-weighted images:

    • Normal tendon: low signal (dark band)

    • Muscle belly: intermediate signal

    • Tendon injuries or degeneration: intermediate-to-bright signal changes at insertion to FDL

  • T2-weighted images:

    • Normal tendon: low signal (dark), darker than T1

    • Muscle belly: intermediate-to-dark

    • Tears: bright linear hyperintense defects within tendon substance

    • Tendinopathy: tendon thickening with patchy hyperintensity

  • STIR:

    • Normal tendon: dark

    • Pathology: bright hyperintense signal indicating edema, inflammation, or tear

  • Proton Density Fat-Saturated (PD FS):

    • Normal tendon: uniformly dark

    • Tendinopathy or tear: focal bright signal in tendon fibers

    • Best sequence for detecting subtle partial tears

  • T1 Fat-Sat Post-Contrast:

    • Normal tendon: minimal or no enhancement

    • Inflammatory tendinitis or post-surgical scarring: enhancement around tendon

CT Appearance

Non-Contrast CT:

  • Tendon visualized as a fine soft-tissue density structure near calcaneus and FDL

  • Difficult to distinguish from surrounding plantar soft tissues

  • Chronic tendinopathy may show calcification or ossification

Post-Contrast CT (standard):

  • Normal tendon does not enhance

  • Peritendinous inflammation may show enhancement

  • Useful in post-surgical follow-up or to assess plantar soft-tissue masses

MRI image

Quadratus Plantae Tendon axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

Quadratus Plantae Tendon axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00001

MRI image

Quadratus Plantae Tendon axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000_00002

CT image

Quadratus Plantae Tendon ct axial image