Explore Anatomy
LT

Lesser Tubercle of Humerus

Lesser tubercle of the humerus is a medial bony prominence that serves as the subscapularis insertion.

RegionUpper Limb
SystemMusculoskeletal System

The lesser tubercle of the humerus is a small but prominent bony projection located on the anterior aspect of the proximal humerus. It serves as a key attachment site for the subscapularis muscle, one of the four rotator cuff muscles. Despite its smaller size compared to the greater tubercle, the lesser tubercle plays a critical role in shoulder stability and internal rotation of the arm.

Location

The lesser tubercle is situated on the anterior surface of the proximal humerus, just medial to the greater tubercle and anterior to the anatomical neck. It lies inferior to the head of the humerus and adjacent to the intertubercular sulcus (also known as the bicipital groove).

Bone Humerus
Position Anterior, proximal humerus
Primary Attachment Subscapularis muscle
Adjacent Structures Intertubercular sulcus (laterally), humeral head (superiorly)

Structure

  • A small, rounded bony prominence located anteriorly on the upper humerus.
  • Roughened surface that provides a strong tendon insertion point.
  • Separated from the greater tubercle by the intertubercular sulcus, which houses the long head of the biceps brachii tendon.

Function

  • Muscle attachment: Serves as the sole insertion point for the subscapularis muscle, which performs internal rotation of the shoulder.
  • Shoulder stability: Acts as part of the bony structure that supports the anterior portion of the glenohumeral joint capsule.
  • Anatomical landmark: Important reference point during shoulder surgery and imaging studies.

Physiological Role(s)

  • Supports medial rotation of the arm via the subscapularis muscle during functional activities such as reaching behind the back or tucking in a shirt.
  • Provides anterior stabilization of the shoulder joint, particularly during activities requiring forward pushing or lifting.
  • Maintains the proper gliding path for the biceps tendon through its relation to the intertubercular groove.

Relations

  • Medially: Head of the humerus and neck of the humerus.
  • Laterally: Intertubercular sulcus and greater tubercle.
  • Anteriorly: Subscapularis tendon crosses and inserts here.
  • Superiorly: Capsule of the glenohumeral joint attaches nearby.

Muscle Attachment

  • Subscapularis: Inserts directly into the lesser tubercle. This is the only muscle that attaches to this tubercle.
  • Contraction of the subscapularis allows for medial (internal) rotation of the arm and contributes to joint stability during movement.

Development

The lesser tubercle develops through endochondral ossification as part of the proximal humeral epiphysis. Ossification centers for the humeral head, greater tubercle, and lesser tubercle typically appear during early childhood. The lesser tubercle fuses with the humeral shaft by the end of puberty. Growth is influenced by muscle tension, particularly from the developing subscapularis muscle.

Clinical Significance

  • Fractures: Isolated fractures of the lesser tubercle are rare but can occur due to avulsion injuries from sudden, forceful contraction of the subscapularis. These may result in shoulder weakness or internal rotation deficit.
  • Rotator cuff tears: Subscapularis tendon tears may involve the insertion site at the lesser tubercle. Such injuries can compromise shoulder function and require surgical repair.
  • Shoulder dislocations: Anterior shoulder dislocations may involve damage to the lesser tubercle or avulsion of the subscapularis tendon.
  • Calcific tendinitis: Calcium deposits may occur at the subscapularis insertion, causing pain and limited shoulder motion.

Imaging

  • X-ray: The lesser tubercle is best visualized in an internal rotation view of the shoulder. It appears as a bony prominence anterior to the humeral head.
  • CT scan: Offers detailed visualization of bony architecture and is useful for evaluating complex fractures or planning surgery.
  • MRI: Preferred modality for assessing soft tissue integrity, especially in suspected subscapularis tendon tears or inflammation.
  • Ultrasound: May assist in dynamic evaluation of the subscapularis tendon and its insertion on the lesser tubercle.

Anatomical Variations

  • Size and prominence of the lesser tubercle may vary slightly among individuals, which can affect surgical landmark identification.
  • Ossification timing may differ in pediatric patients, making radiographic interpretation age-dependent.
  • In cases of developmental dysplasia or congenital anomalies, the tubercle may be malformed or hypoplastic.
Published on May 12, 2025
Disclaimer: The content on this site is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.