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Lesser tubercle of humerus

The lesser tubercle of the humerus (tuberculum minus) is a small, prominent anterior projection of the proximal humerus, located medial to the greater tubercle and separated from it by the intertubercular sulcus (bicipital groove). It serves as the insertion site for the subscapularis muscle, one of the four rotator cuff muscles responsible for internal rotation of the arm.

It lies anteriorly and slightly medially, forming a palpable bony landmark deep to the deltoid and pectoralis major. The lesser tubercle contributes to shoulder stability and internal rotation, particularly during arm adduction and overhead movements.

Synonyms

  • Tuberculum minus humeri

  • Lesser tuberosity of humerus

Location and Structure

  • Position: Anterior and medial aspect of the proximal humerus, adjacent to the head.

  • Shape: Rounded and prominent anterior bony projection.

  • Borders:

    • Lateral: Intertubercular sulcus (bicipital groove)

    • Medial: Blends into humeral shaft

    • Superior: Continuous with the humeral head

    • Inferior: Marks the transition to the humeral shaft

  • Surface: Roughened anteriorly for subscapularis tendon attachment; smooth posteriorly beneath the shoulder capsule.

Relations

  • Anteriorly: Deltoid and pectoralis major muscles

  • Posteriorly: Shoulder joint capsule and synovial membrane

  • Medially: Humeral head

  • Laterally: Intertubercular sulcus containing the tendon of the long head of the biceps brachii

  • Superiorly: Subscapularis tendon insertion blending with joint capsule

Attachments

  • Subscapularis muscle: Entire anterior surface of the lesser tubercle — primary tendon insertion providing internal rotation of the humerus.

  • Joint capsule: Partly attaches superiorly at the margin of the tubercle.

  • Bicipital bursa: Lies between the subscapularis tendon and the anterior capsule to reduce friction.

Nerve Supply

  • Subscapularis muscle: Supplied by upper and lower subscapular nerves (C5–C6), branches of the posterior cord of the brachial plexus.

Function

  • Muscle attachment: Provides insertion for the subscapularis tendon.

  • Internal rotation: Acts as the key bony lever for medial rotation of the humerus.

  • Stabilization: Helps maintain humeral head position in the glenoid cavity during motion.

  • Protection: Serves as an anterior buttress, shielding the humeral head and shoulder joint capsule.

Clinical Significance

  • Fractures: Isolated fractures are rare but may occur with anterior shoulder dislocation or direct trauma.

  • Avulsion injuries: Can result from violent contraction or rupture of the subscapularis tendon.

  • Subscapularis tendinopathy: Common degenerative or traumatic pathology associated with anterior shoulder pain and weakness in internal rotation.

  • Post-surgical relevance: Used as a landmark in shoulder arthroplasty and rotator cuff repair.

  • Imaging importance: MRI and CT evaluate tendon insertion, avulsion, bone marrow edema, and cortical integrity.

MRI Appearance

  • T1-weighted images:

    • Cortex: Low signal (dark), sharply defined.

    • Marrow: Bright, fatty signal in normal bone.

    • Subscapularis tendon: Low signal attaching to anterior surface.

    • Bicipital groove: Low-signal band lateral to tubercle (biceps tendon).

    • Fracture or avulsion: Linear low-signal defect; adjacent marrow edema appears intermediate-to-bright.

  • T2-weighted images:

    • Cortex: Low signal.

    • Marrow: Bright, slightly less intense than on T1.

    • Tendon insertion: Low signal; bright hyperintensity indicates tendinopathy or tear.

    • Bursa: May show hyperintense fluid between subscapularis and capsule in bursitis.

    • Pathology: Avulsion or subscapularis tear shows fluid signal at tendon attachment with cortical irregularity.

  • STIR:

    • Normal marrow: Intermediate-to-dark signal.

    • Pathologic marrow (edema, fracture, osteitis): Bright hyperintensity extending from cortical margin.

    • Sensitive for subtle bone bruising or early subscapularis insertional inflammation.

  • Proton Density Fat-Saturated (PD FS):

    • Normal marrow: Intermediate-to-dark.

    • Abnormal: Bright signal along subscapularis footprint indicating tendinopathy, partial tear, or bursitis.

    • Excellent for delineating peritendinous fluid and insertional pathology.

  • T1 Fat-Sat Post-Contrast:

    • Normal bone: Mild homogeneous enhancement.

    • Inflamed tendon/bursa: Shows focal or diffuse enhancement.

    • Tear or avulsion: Peripheral rim enhancement with central non-enhancing gap or hematoma.

CT Appearance

Non-Contrast CT:

  • Cortex: High attenuation with smooth anterior contour.

  • Trabecular bone: Bright fatty marrow density.

  • Subscapularis insertion: Seen as subtle roughening or cortical thickening at anterior prominence.

  • Pathology: Detects avulsion fractures, cortical irregularity, sclerosis, or small bony fragments.

Post-Contrast CT (standard):

  • Normal bone: Uniform enhancement of marrow.

  • Inflammation or tendon avulsion: Adjacent soft-tissue enhancement and fat stranding.

  • Useful for evaluating postoperative repair sites, calcific tendinitis, and cortical erosion.

CT VRT 3D image

Lesser tubercle of humerus 3d vrt image

MRI image

Lesser tubercle of humerus axial cross sectional anatomy 3T MRI AI enhanced radiology image-img-00000-00000

CT image

Lesser tubercle of humerus ct axial image

CT image

Lesser tubercle of humerus ct sag image