Humerus Bone Labelled: Complete Anatomical Guide And Diagram Reference (2026)

The humerus is the longest and largest bone of the upper limb, serving as the structural framework for the brachium and orchestrating critical biomechanical transitions between the shoulder girdle and the forearm. This guide provides a systematic, labelled osteological mapping of the proximal epiphysis, diaphysis, and distal epiphysis according to current Terminologia Anatomica standards.

Understanding the bony landmarks of the humerus is essential for clinical diagnosis, musculoskeletal palpation, cross-sectional radiographic interpretation, and orthopedic fracture fixation.

Proximal Humeral Epiphysis: Articular and Tubercular Landmarks

The proximal humerus forms the glenohumeral articulation and serves as the insertion platform for the dynamic stabilizing musculature of the rotator cuff. Its morphology is characterized by distinct articular, non-articular, and transitional zones.

+-------------------------------------------------------------+ | Proximal Landmarks at a Glance: | | - Humeral Head | | - Anatomical Neck | | - Greater Tubercle (Superior, Middle, Inferior Facets) | | - Lesser Tubercle | | - Intertubercular Sulcus (Bicipital Groove) | | - Surgical Neck | +-------------------------------------------------------------+

(Diagrammatic reference: Refer to clinical osteology models for spatial correlation.)

1. Humeral Head (Caput Humeri)

The humeral head presents a smooth, hemispherical articular surface directed medially, superiorly, and posteriorly toward the glenoid cavity of the scapula. It is covered in hyaline cartilage, which is thickest at the center and thins toward the margins. In the standard anatomical position, its retroversion angle averages 20 to 30 degrees relative to the transepicondylar axis of the distal humerus.

2. Anatomical Neck (Collum Anatomicum)

Circling the head obliquely is the anatomical neck, an indentation demarcating the boundary between the articular cartilage and the non-articular bony tissue of the tubercles. It serves as the primary attachment zone for the fibrous joint capsule of the glenohumeral joint.

3. Greater Tubercle (Tuberculum Majus)

Positioned laterally on the proximal end, the greater tubercle features three distinct flat muscular impressions or facets:

• Superior Facet: Insertion site for the supraspinatus tendon.
• Middle Facet: Insertion site for the infraspinatus tendon.
• Inferior Facet: Insertion site for the teres minor tendon.

4. Lesser Tubercle (Tuberculum Minus)

Positioned anteriorly, medial to the greater tubercle, the lesser tubercle provides the broad insertion point for the subscapularis muscle. It marks the medial perimeter of the upper humeral shaft.

5. Intertubercular Sulcus (Sulcus Intertubercularis / Bicipital Groove)

A vertical indentation separating the greater and lesser tubercles. It accommodates the tendon of the long head of the biceps brachii accompanied by its synovial sheath and an ascending branch of the anterior humeral circumflex artery. The margins of this groove form distinct crests:

• Lateral Lip (Crista Tuberculi Majoris): Provides the anchor point for the pectoralis major tendon.
• Floor: Receives the broad terminal tendon of the latissimus dorsi.
• Medial Lip (Crista Tuberculi Minoris): Anchorage point for the teres major tendon.

6. Surgical Neck (Collum Chirurgicum)

The tapered constriction located immediately distal to the greater and lesser tubercles. This junctional zone between the proximal epiphysis and the tubular shaft represents a frequent site of clinical fractures. Closely applied to the posterior and lateral aspect of the surgical neck are the axillary nerve and the posterior humeral circumflex artery within the quadrangular space.

Humeral Shaft (Diaphysis) Topography and Pathways

The shaft of the humerus changes structurally along its longitudinal axis, starting cylindrical proximally and flattening into a triangular prism distally. It presents three distinct borders (anterior, lateral, medial) and three surfaces (anteromedial, anterolateral, posterior).

+-------------------------------------------------------------+ | Shaft Landmarks at a Glance: | | - Deltoid Tuberosity | | - Radial Groove (Sulcus Nervi Radialis / Spiral Groove) | | - Medial Supracondylar Ridge | | - Lateral Supracondylar Ridge | +-------------------------------------------------------------+

Deltoid Tuberosity

Situated midway down the anterolateral surface, this rough, raised, V-shaped prominence serves as the distal insertion site for the multipennate fibers of the deltoid muscle.

Radial (Spiral) Groove

Winding obliquely down the posterior and posterolateral surface of the midshaft is the radial groove. It courses downward and outward behind the deltoid tuberosity, transmitting:

• The radial nerve (C5–T1 roots).
• The profunda brachii artery (deep brachial artery) and accompanying venae comitantes. The medial and lateral heads of the triceps brachii muscle originate on the bony surfaces immediately inferior and superior to this groove, respectively.

Supracondylar Ridges

Toward the distal third of the diaphysis, the medial and lateral borders sharpen into the medial and lateral supracondylar ridges. The lateral ridge is significantly more pronounced, serving as the proximal attachment for the brachioradialis and the extensor carpi radialis longus muscles.

Distal Humeral Epiphysis: Articular Complex and Fossae

The distal humerus broadens transversely to form the humeral condyle, which features both non-articular projections (epicondyles) and precision-molded articular surfaces for the radius and ulna.

+-------------------------------------------------------------+ | Distal Landmarks at a Glance: | | - Medial Epicondyle and Ulnar Sulcus | | - Lateral Epicondyle | | - Capitulum (Lateral Articulation) | | - Trochlea (Medial Articulation) | | - Radial Fossa | | - Coronoid Fossa | | - Olecranon Fossa | +-------------------------------------------------------------+

Articular Complex

• Capitulum: A smooth, rounded, hemispherical eminence positioned on the lateral distal surface. It articulates exclusively with the concave articular fovea on the head of the radius.
• Trochlea: A pulley-shaped medial surface spanning both the anterior and posterior compartments of the distal humerus. It articulates with the trochlear notch of the ulna. Its medial margin projects lower than the lateral margin, creating the natural outward deviation of the extended forearm known as the carrying angle (typically 10 to 15 degrees in males, 15 to 20 degrees in females).

Fossae of the Distal Humerus

• Radial Fossa: A shallow depression located anteriorly above the capitulum that receives the anterior margin of the radial head during full elbow flexion.
• Coronoid Fossa: A small depression situated anteriorly above the trochlea that accommodates the coronoid process of the ulna during active flexion.
• Olecranon Fossa: A large, deep, triangular depression situated posteriorly above the trochlea. It accepts the hooked olecranon process of the ulna when the elbow reaches terminal extension. A thin plate of bone separates the olecranon fossa from the coronoid fossa anteriorly, which can occasionally be perforated to form a supratrochlear foramen.

Epicondyles

• Medial Epicondyle: A large, blunt projection pointing medially. It serves as the common origin for the superficial forearm flexors (pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris, and flexor digitorum superficialis) and the ulnar collateral ligament. The posterior surface of the medial epicondyle is grooved by the sulcus for the ulnar nerve.
• Lateral Epicondyle: Smaller and less prominent than its medial counterpart, this lateral projection gives origin to the common forearm extensor tendon (including extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris), the supinator, and the radial collateral ligament.

Complete Landmark, Muscular, and Neurovascular Reference

The following table synthesizes the primary anatomical zones, precise labelled landmarks, clinical associations, and soft-tissue attachments across the humerus.

Clinical Correlations: Fractures, Nerve Injuries, and Diagnostics

The close proximity of major peripheral nerves to specific bony landmarks makes humeral fractures particularly prone to characteristic neurological deficits.

+-------------------------------------------------------------+ | Critical Nerve Vulnerability Zones: | | 1. Surgical Neck Fracture --> Axillary Nerve | | 2. Midshaft Fracture --> Radial Nerve (Wrist Drop) | | 3. Medial Epicondyle Injury --> Ulnar Nerve (Claw Hand) | | 4. Supracondylar Fracture --> Median Nerve / Brachial A. | +-------------------------------------------------------------+

Proximal Fractures and the Neer Classification

Proximal humeral fractures are evaluated using the four-segment Neer Classification system. The four segments correspond directly to the anatomical landmarks:

1. Humeral head
2. Greater tubercle
3. Lesser tubercle
4. Humeral shaft

A part is considered displaced only if there is more than 1 centimeter of separation or greater than 45 degrees of angulation. Fractures through the surgical neck risk damaging the axillary nerve, leading to paralysis of the deltoid and teres minor alongside sensory loss over the "sergeant's patch" on the lateral shoulder. Additionally, severe displacement of the anatomical neck threatens the blood supply to the humeral head via the arcuate artery, leading to avascular necrosis (AVN).

Midshaft Humeral Fractures and Radial Nerve Palsy

Fractures of the diaphysis, especially spiral fractures at the junction of the middle and distal thirds (Holstein-Lewis fractures), place the radial nerve at high risk of stretch, entrapment, or laceration within the spiral groove.

• Motor Deficit: Loss of wrist extension, finger extension at the metacarpophalangeal joints, and thumb abduction (manifesting as classic "wrist drop").
• Sensory Deficit: Paresthesia or anesthesia over the first dorsal web space on the dorsum of the hand.

Clinical Management Note:

Most closed humeral shaft fractures with neuropraxia of the radial nerve are managed non-operatively with functional bracing (Sarmiento brace). Up to 90% of closed radial nerve neuropraxias resolve spontaneously within 3 to 4 months. Immediate surgical exploration is indicated in open fractures, secondary palsies developing after reduction, or irreducible fractures.

Distal Humeral and Supracondylar Fractures

Common in pediatric populations, supracondylar fractures occur directly superior to the condyles and epicondyles. Displaced extension-type injuries threaten:

• The brachial artery, which can lead to ischemic contracture of the forearm flexor compartment (Volkmann ischemic contracture).
• The anterior interosseous nerve (a motor branch of the median nerve), resulting in an inability to perform the "OK" sign (weakness of flexor pollicis longus and flexor digitorum profundus to the index finger).
• Fractures or avulsions of the medial epicondyle can directly stretch or shear the ulnar nerve, leading to motor weakness in the intrinsic muscles of the hand and numbness along the small finger and medial ring finger.

Palpation Protocol for Clinical and Anatomical Examination

Examining the humerus in a clinical setting requires step-by-step palpation using reliable bony landmarks to confirm structural integrity and joint alignment:

1. Locate the Acromion: Trace the bony shelf of the scapular spine laterally until reaching the lateral edge of the acromion.
2. Palpate the Greater Tubercle: Move your fingers approximately one centimeter inferior to the anterolateral margin of the acromion. Passively rotate the patient's forearm internally and externally to feel the greater tubercle roll beneath your fingertips.
3. Trace the Intertubercular Sulcus: Move your fingers slightly medial from the greater tubercle. With the arm in slight external rotation, the tendon of the long head of the biceps can be palpated within the bicipital groove.
4. Identify the Lesser Tubercle: Palpate medially past the groove; internal rotation brings the lesser tubercle directly forward under the examiner's thumb.
5. Palpate the Distal Epicondyles: Move distally down the arm to the elbow. Grasp the medial and lateral aspects of the elbow simultaneously. The medial epicondyle is prominent and sharp; the lateral epicondyle is flatter and more rounded.
6. Evaluate the Triangle of the Elbow: With the elbow flexed to 90 degrees, confirm that the medial epicondyle, lateral epicondyle, and the tip of the olecranon form an equilateral triangle. In full elbow extension, these three landmarks should align in a straight horizontal line. A disruption of this relationship indicates elbow dislocation or an intra-articular condylar fracture.

Frequently Asked Questions

Which nerve is damaged in a midshaft humerus fracture?

The radial nerve is the most frequently injured nerve in a midshaft humerus fracture because it runs directly along the bone in the radial (spiral) groove. Injury results in wrist drop, an inability to extend the fingers at the metacarpophalangeal joints, and sensory loss over the first dorsal web space.

What is the difference between the anatomical neck and surgical neck of the humerus?

The anatomical neck is the slight constriction directly circumscribing the articular margin of the humeral head, serving as the attachment for the glenohumeral joint capsule. The surgical neck is the narrower area located distal to the greater and lesser tubercles. It is called the surgical neck because it is a common site of fracture requiring surgical intervention, and it is closely related to the axillary nerve.

What muscles attach to the greater tubercle of the humerus?

Three rotator cuff muscles insert onto the greater tubercle: the supraspinatus (superior facet), the infraspinatus (middle facet), and the teres minor (inferior facet). Together, these muscles provide abduction and external rotation of the arm while dynamically stabilizing the humeral head in the glenoid fossa.

What is the carrying angle formed by the humerus?

The carrying angle is the physiological outward angle formed between the anatomical axis of the humerus and the ulna when the arm is fully extended and supinated. It is created by the oblique alignment of the trochlea, where the medial lip projects farther distally than the lateral lip. It measures roughly 10 to 15 degrees in males and 15 to 20 degrees in females to allow the arm to swing clear of the pelvis during gait.

What structure runs in the bicipital groove of the humerus?

The tendon of the long head of the biceps brachii, enclosed within its synovial sheath, passes through the bicipital groove (intertubercular sulcus). It is accompanied by the ascending branch of the anterior humeral circumflex artery and is held in place by the transverse humeral ligament and fibers of the subscapularis and pectoralis major insertions.

Advanced Diagnostic and Anatomical Training

Mastery of the labelled humerus provides the foundation for evaluating complex pathologies, from sports-related rotator cuff tears to complex distal articular reconstructions. For clinicians, physical therapists, and medical trainees, pairing surface anatomy palpation with cross-sectional imaging (CT and 3T MRI) reinforces these bony landmarks and their direct soft-tissue relationships.