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Conoid ligament

The conoid ligament is the posteromedial component of the coracoclavicular ligament, which connects the clavicle to the coracoid process of the scapula. It plays a crucial role in stabilizing the acromioclavicular (AC) joint, preventing excessive superior displacement of the clavicle relative to the scapula.

It is a dense fibrous band, roughly triangular in shape, with its apex attached to the coracoid process and its base attached to the clavicle. The conoid ligament works synergistically with the trapezoid ligament (its anterolateral counterpart) to maintain vertical and rotational stability of the clavicle during shoulder motion.

Synonyms

  • Posteromedial coracoclavicular ligament

  • Medial division of coracoclavicular ligament

Location and Structure

  • Component: Medial and posterior part of the coracoclavicular ligament complex

  • Shape: Triangular or cone-shaped; apex inferior, base superior

  • Fibers: Dense, collagenous, arranged vertically between coracoid process and clavicle

Attachments

  • Inferior attachment: Root of the coracoid process of the scapula, near its base

  • Superior attachment: Conoid tubercle and adjacent posterior border of the inferior surface of the clavicle

  • Orientation: Fibers run almost vertically upward and laterally from coracoid to clavicle

Relations

  • Anteriorly: Trapezoid ligament (the anterolateral part of coracoclavicular ligament complex)

  • Posteriorly: Suprascapular artery and nerve (separated by fascia)

  • Superiorly: Clavicle and deltotrapezial fascia

  • Inferiorly: Coracoid process and insertion of coracoclavicular fascia

  • Laterally: Continuous with the trapezoid ligament near the clavicular attachment

Nerve Supply

  • Supraclavicular nerves (sensory fibers from cervical plexus, C3–C4)

  • Branches of the subclavian nerve plexus may provide minor proprioceptive innervation

Function

  • Primary stabilizer of the acromioclavicular joint in the vertical plane

  • Prevents upward displacement of the clavicle relative to the scapula

  • Acts as a suspension structure, maintaining the scapula in alignment with the thoracic wall

  • Restrains axial rotation and separation of the clavicle during shoulder elevation

  • Synergistic role: Works with trapezoid ligament to transmit load between clavicle and scapula

Clinical Significance

  • AC joint separation: Injury to the conoid ligament occurs in Grade III and higher AC separations, leading to clavicular elevation and scapular droop

  • Ligament rupture: Causes instability of the coracoclavicular complex and superior translation of the clavicle

  • Surgical relevance: Repair or reconstruction (e.g., Weaver-Dunn procedure, anatomical CC reconstruction) essential for restoring shoulder girdle mechanics

  • Calcification or ossification: May be seen after chronic injury or enthesopathy

  • Imaging importance: MRI and CT are vital for assessing partial or complete tears, post-traumatic displacement, and reconstruction integrity

MRI Appearance

  • T1-weighted images:

    • Normal ligament: Low signal (dark), sharply marginated fibrous band between coracoid and clavicle

    • Adjacent bone marrow: Bright on T1 due to fatty composition

    • Pathology: Partial tear — focal thickening or wavy low-signal fibers with surrounding intermediate signal; complete tear — discontinuity with adjacent bright signal from hematoma or edema

  • T2-weighted images:

    • Normal: Low signal intensity, homogeneous dark band

    • Acute injury: High-signal intensity between ligament ends or within surrounding soft tissue

    • Chronic injury: Thinned or irregular low-signal fibers with small areas of intermediate signal indicating fibrosis

    • Marrow edema at attachment sites appears hyperintense

  • STIR:

    • Normal: Low-to-intermediate signal

    • Tear or inflammation: Bright hyperintense signal due to edema or hemorrhage around the ligament

    • Excellent for detecting early or subtle coracoclavicular ligament sprains

  • Proton Density Fat-Saturated (PD FS):

    • Normal: Thin, dark linear structure between clavicle and coracoid

    • Partial tear: Focal bright areas within or adjacent to the ligament

    • Complete tear: Discontinuity with fluid-bright gap and associated surrounding edema

  • T1 Fat-Sat Post-Contrast:

    • Normal ligament: No significant enhancement

    • Inflamed or healing ligament: Peripheral or diffuse enhancement due to granulation tissue

    • Chronic scarring: Minimal or rim-like enhancement with low-signal fibrosis in mature lesions

CT Appearance

Non-Contrast CT:

  • Normal: Ligament not directly visualized; appears as soft-tissue density band between coracoid base and conoid tubercle

  • Bony attachments: Conoid tubercle and coracoid base clearly identified

  • Pathology: Avulsion fractures, calcifications, or post-traumatic ossification may be visible

  • Chronic stress: May show bony remodeling at attachment sites

Post-Contrast CT (standard):

  • Normal ligament: Poorly defined; surrounding fascia enhances slightly

  • Acute injury: Enhancing soft tissue or hematoma at coracoclavicular interval

  • Reconstruction assessment: Visualizes fixation hardware, graft placement, and postoperative complications

MRI image

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

MRI image

Conoid ligament coronal cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

MRI image

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

CT image

Conoid ligament ct coronal