Last Updated on May 24, 2025
The humerus is the longest and largest bone of the upper limb. It connects the shoulder to the elbow, acting as a vital link between the axial and appendicular skeletons. The anatomical structure of the humerus is central not only to daily actions like lifting, throwing, and writing, but also to the stability and mobility of the entire upper limb.
Understanding the anatomy of the humerus is essential for diagnosing and managing upper limb fractures, nerve injuries, and various orthopedic conditions. The bone also serves as a key site for muscle, tendon, and ligament attachments.
Structure of the Humerus Bone
For anatomical description, the humerus is typically divided into three main parts:
- Proximal end
- Shaft
- Distal end
Proximal End of Humerus
The proximal end of the humerus consists of a head, an anatomical neck, and the greater & lesser tubercles and intertubercular sulcus. [See figure below – Proximal Humerus Anatomy]
Head
The head is the most proximal region of the bone. It is almost spherical in shape and flattens slightly where it attaches to the scapula and clavicle.
The head is directed medially, backward, and upwards. It articulates with the glenoid cavity of the scapula to form the shoulder joint. The head forms about one-third of a sphere and is much larger than the glenoid cavity.
The line separating the head from the rest of the upper end is called the anatomical neck.
It is marked by a slight narrowing below the articular surface of the head and serves as the capsular attachment for the shoulder joint, thus providing a greater range of mobility.
Clinical Note: The fractures of the head are not very common but are often associated with high trauma and can compromise shoulder function
Greater tubercle
The greater tubercle is an elevation that forms the lateral part of the upper end. It is the most lateral part of the proximal end of the humerus.
It has three impressions at the posterosuperior region for supraspinatus, infraspinatus, and teres minor from above downward.
It also contains multiple vascular foramina.
Clinical note: Fractures of the greater tubercle can lead to rotator cuff dysfunction.
Lesser tubercle
The lesser tubercle is an elevation on the anterior aspect of the upper end. The lesser tubercle is located anterior to the anatomical neck. Laterally, it forms the medial margin of the intertubercular sulcus. It serves as the attachment for the subscapularis muscle and the transverse ligament of the shoulder.
Intertubercular sulcus
The intertubercular sulcus or bicipital groove is an indentation located between the two tubercles. The sulcus consists of a lateral lip formed by the crest of the greater tubercle and a medial lip formed by the lateral aspect of the lesser tubercle.
The floor of the sulcus contains the long head of the biceps tendon and the ascending branch of the anterior circumflex humeral artery. The intertubercular sulcus has 3 important attachments. The latissimus dorsi muscle attaches to the floor. The pectoralis major is on the lateral lip, and the teres major is on the medial lip.
Surgical neck
The line separating the upper end of the humerus from the shaft is called the surgical neck and is marked by a slight narrowing. It is a common site of injury in elderly people.
Do You Know?
The surgical neck is called so because it is a common site for fractures and hence the focus of the surgeons
Shaft of Humerus
The shaft is rounded in the upper half and triangular in the lower half. It has three borders and three surfaces.
Borders
Anterior Border: It is a continuation of the lateral lip of the intertubercular sulcus or bicipital groove. It runs from the greater tubercle to the lateral epicondyle. The deltoid tuberosity, found on its middle part, serves as the insertion for the deltoid muscle.
Lateral Border: The lateral border extends from the greater tubercle to the lateral epicondyle. The lower part is closely related to the radial nerve as it winds in the radial groove.
Medial Border: It runs from the lesser tubercle, as a continuation of the medial lip of the intertubercular sulcus, to the medial epicondyle. It is less prominent, but the nutrient foramen is usually found here. In its middle, it presents a rough strip. It is continuous below with the medial supracondylar ridge.
Surfaces
Anterolateral Surface: The anterolateral surface lies between the anterior and lateral borders. The deltoid covers the upper half of this surface.
It is marked by a V-shaped deltoid tuberosity, a little above the middle.
This tuberosity is the insertion of the deltoid muscle around the middle of the surface, and the lateral distal portion is the origin of the brachialis muscle (along with the proximal two-thirds of the lateral supracondylar ridge.
Anteromedial Surface: It lies between the anterior and medial borders. Its upper one-third is narrow and forms the floor of the bicipital groove.
Near the medial border, at almost the middle, a nutrient foramen is seen. The coracobrachialis muscle attaches to it around its middle, and the distal half of the surface is mainly covered by the medial part of the brachialis.
Posterior Surface: I lies between the medial and lateral borders. It is marked by an oblique ridge in the upper part and is crossed by the radial groove in the middle third.
The lateral head of the triceps muscle originates from the ridge on the proximal third. Most of the lower half of the posterior surface provides origin to the medial head of triceps.
Clinical note: Fractures at the mid-shaft may endanger the radial nerve, leading to wrist drop.
Important Landmarks of the Shaft of Humerus
| Landmark | Location | Clinical/Anatomical Significance |
|---|---|---|
| Deltoid Tuberosity | Lateral aspect, mid-shaft | Insertion site for the deltoid muscle |
| Radial Groove | Posterior surface, oblique course | Entry point for the nutrient artery supplying the bone |
| Nutrient Foramen | Anteromedial surface, mid to lower shaft | Entry point for nutrient artery supplying the bone |
Lower/Distal End of Humerus
Below the deltoid tuberosity, the humerus gradually widens, doubling its width as it approaches the elbow.
The lower end of the humerus forms the condyles. This end expanded from side to side and shows a lateral supracondylar ridge on the lateral side and a medial supracondylar ridge on the medial side.
The distal end consists of both articular and non-articular parts.
Articular Part
The articular part of the humerus articulates with both the ulna and radius. It consists of a medial trochlea and a lateral capitellum. A faint groove separates them.
Trochlea
The trochlea is a pulley-shaped surface. It articulates with the trochlear notch of the ulna to form the elbow joint.
The medial edge of the trochlea projects down 6 mm more than the lateral edge, leading to the carrying angle or the angle that the forearm makes with the humerus.
The trochlea covers the anterior, posterior, and inferior surfaces of the medial condyle of the humerus.
During the extension of the elbow, the posterior and inferior aspects of the trochlea are in contact with the ulna.
On flexion, the trochlear notch slides towards the anterior and the posterior part is not in contact.
Capitellum
The capitellum is a convex, rounded projection that articulates with the head of the radius to form a radiocapitellar joint.
It covers the anterior and inferior surfaces of the lateral condyle of the humerus, but doesn’t cover the posterior surface as the trochlea does.
Nonarticular part
The non-articular part has the medial and lateral epicondyles, the olecranon fossa, the coronoid fossa, and the radial fossa.
- Medial Epicondyle: The medial epicondyle is where the medial border ends and appears as a projection superomedial to the medial condyle. The ulnar nerve passes posterior to it and is palpable against it. It serves as the origin of the superficial flexor muscles of the wrist and hand.
- Lateral Epicondyle: The lateral border of the humerus ends at the lateral epicondyle. It serves as an origin to the extensor compartment muscles of the wrist and hand
- Coronoid fossa: It is an anterior depression just above the anterior aspect of the trochlea to accommodate the coronoid process of the ulna when the elbow is flexed.
- Radial fossa: It is a depression present just above the anterior aspect of the capitellum and accommodates the head of the radius when the elbow is flexed.
- Olecranon fossa: This lies posteriorly above the trochlea. It is a big fossa that lodges the tip of the olecranon into this fossa.
Attachments
Proximal Humerus
- Lesser tubercle: The subscapularis muscle is inserted
- Greater tubercle: From above down
- Supraspinatus on uppermost part
- Infraspinatus – Middle
- Teres minor- lower part
- Intertubercular sulcus:
- Pectoralis major inserts into the lateral lip
- Teres major is inserted into the medial lip
- Latissimus dorsi is inserted into the floor
- Anatomical neck: Capsular ligament of the shoulder joint, except on the medial side. On the medial side, the attachment line dips down by about a centimeter to include a small area of the shaft within the joint cavity. An aperture is provided for the tendon of the long head of the biceps leave the joint cavity
Shaft of Humerus
The deltoid tuberosity provides insertion for the deltoid muscle.
A rough area in the middle of the medial border is for the insertion of the coracobrachialis.
The brachialis arises from the lower halves of the anteromedial and anterolateral surfaces of the shaft, extending in part onto the posterior aspect.
Distal Humerus
Lateral side
The upper two-thirds of the lateral supracondylar ridge gives origin to brachioradialis, whereas the lower one-third gives rise to extensor carpi radialis longus.
The common extensor origin on the lateral epicondyle provides origin to the extensor muscles of the forearm. These muscles are
- Brachioradialis
- Extensor carpi radialis longus
- Extensor carpi radialis brevis
- Extensor digitorum
- Extensor digiti minimi
- Extensor carpi ulnaris.
Medial Side
The anteromedial surface, near the lower end of the medial supracondylar ridge, gives origin to the humeral head of the pronator teres. The other end arises from the ulna on the medial side of the coronoid.
The posterior surface of the lateral epicondyle gives rise to the anconeus muscle.
The common flexor origin on the anterior aspect of the medial epicondyle gives rise to superficial flexors of the wrist and hand, commonly called flexor forearm muscles. These are
- Flexor carpi ulnaris
- Palmaris longus
- Flexor carpi radialis
- Pronator teres
[ Read more on muscles of Forearm]
The capsule of the elbow joint is attached along a line that reaches proximal to the radial and coronoid fossae, anteriorly, and on the posterior side, proximal to the olecranon fossa.
On the medial side, the line of attachment of the capsule passes between the medial epicondyle and the trochlea. On the lateral side, it passes between the lateral epicondyle and the capitellum.
Articulations
Proximally, the humerus articulates with the glenoid fossa of the scapula to form the glenohumeral joint or shoulder joint.
[Know more about the shoulder joint]
Distally, the humerus’ lower end forms the humeroulnar joint with the ulna and radiocapitellar joint with the radius, collectively known as the elbow joint.
Side Determination of Humerus Bone
- The upper end is rounded to form the head. The lower end is expanded from side to side and flattened from before backward.
- The head is directed medially and backward.
- The lesser tubercle projects from the front of the upper end and is limited laterally by the intertubercular sulcus (bicipital groove)
Clinical Significance
Fractures of the Humerus
- Proximal Humerus Fractures: Common in older adults, especially with osteoporosis. These fractures often involve the surgical neck and may injure the axillary nerve and posterior circumflex humeral vessels, leading to impaired shoulder abduction.
- Shaft (Diaphyseal) Fractures: Frequently result from direct trauma. Mid-shaft fractures may damage the radial nerve, causing wrist drop and sensory loss over the dorsum of the hand.
- Distal Humerus (Supracondylar) Fractures: Most common in children, usually from falls on an outstretched hand. High risk of neurovascular complications, especially to the median nerve and brachial artery. Malunion can lead to cubitus varus or gunstock deformity.
Nerve Injuries Associated with the Humerus
- Axillary Nerve: It may be injured with surgical neck fractures. It results in deltoid paralysis and sensory loss over the lateral shoulder.
- Radial Nerve: It is vulnerable in the mid-shaft and spiral groove fractures, and the injury leads to wrist drop.
- Ulnar Nerve: The ulnar nerve is susceptible to injury behind the medial epicondyle (especially in elbow trauma), causing sensory and motor deficits in the hand.
- Median Nerve: It can be injured in supracondylar fractures, resulting in thenar muscle weakness and sensory loss in the lateral palm.
Pathological and Metastatic Lesions
- Metastatic Deposits: The humerus is a frequent site for metastasis from cancers such as breast, lung, prostate, and kidney. Lesions may cause pathological fractures.
- Primary Bone Tumors: Less commonly, the humerus can be affected by benign and malignant tumors (e.g., osteosarcoma, enchondroma).
Overuse and Traction Injuries
- Epicondylitis:
- Medial epicondylitis (golfer’s elbow): Inflammation of the common flexor origin.
- Lateral epicondylitis (tennis elbow): Inflammation of the common extensor origin.
Surgical and Orthopedic Relevance
The deltoid tuberosity, radial groove, and epicondyles are critical reference points for surgical approaches and nerve preservation.
Metastatic Disease
The humerus is known for the spread of metastases. The metastases can weaken the bone, leading to pathological fractures.
References
- R.L. Drake, A. Wayne, A.W.M. Mitchell: Gray’s Anatomy For Students, 2nd Edition, Churchill Livingstone (2010), p.997-1000, 1035-6, 1053-4.
- Capo JT, Criner KT, Shamian B. Exposures of the humerus for fracture fixation. Hand Clin. 2014 Nov;30(4):401-14, v. [PubMed]
