Last Updated on March 20, 2025
The humerus is a bone that connects the shoulder and elbow. The humerus is the largest bone in the upper limb and the only bone in the upper arm. Humerus movements participate in many daily essential activities like throwing, lifting, writing, and others requiring shoulder joint movements.
Proximally, humerus forms part of the shoulder joint whereas distally, the humerus articulates with the radius and ulna to form the elbow joint.
The humerus bone acts as an attachment site for many important muscles and ligaments.
Structure of Humerus Bone
For describing the anatomy of the humerus bone, it is divided into three 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.
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.
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.
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. Intertubercular sulcus has 3 important attachemtns. The lattisimus 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 slight narrowing.
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
The anterior border is a continuation of the lateral lip of the intertubercular sulcus or bicipital groove. In its middle part, it forms the anterior margin of the deltoid tuberosity. The lower half of the anterior border is smooth and rounded.
The lateral border begins just distal to the greater tubercle of the humerus. The lateral border is prominent only at the lower end where it forms the lateral supracondylar ridge. The middle portion of the lateral border is adjacent to the deltoid tuberosity.In the middle part, it is interrupted by the radial (spiral) groove which holds the radial nerve and deep brachial artery.
The medial lip of the intertubercular sulcus or bicipital groove continues as the medial border. In its middle, it presents a rough strip. It is continuous below with the medial supracondylar ridge.
Surfaces
The anterolateral surface lies between the anterior and lateral borders. The upper half of this surface is covered by the deltoid. 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.
The anteromedial surface 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.
Between the medial and lateral borders lies the posterior surface. 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 posterior surface provides origin to medial head of triceps.
Lower 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 condyle which is expanded from side to side and shows a lateral supracondylar ridge on lateral side and the medial supracondylar ridge is a similar ridge on the medial side.
Distal end
The distal end consists of both articular and non-articular parts. 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.
The non-articular part has the medial and lateral epicondyles, the olecranon fossa, the coronoid fossa, and the radial fossa.
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 posterior art 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
- Medial Epicondyle: The medial epicondyle is where the medial border ends and appears as a projection superomedial to the medial condyle. it i an important landmark as the ulnar nerve passes posterior to it and is palpable against it. It serves as an origin of 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 tip of lodges into this fossa.
Attachments
Proximal Humerus
- Lesser tubercle: 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 leaves the joint cavity
Shaft of Humerus
The deltoid tuberosity provides insertion to the deltoid muscle.
A rough area in the middle of the medial border is for the insertion of coracobrachialis.
The brachialis arises from the lower halves of the anteromedial and anterolateral surfaces of the shaft extending in part on to the posterior aspect.
Distal Humerus
Upper two-thirds of the lateral supracondylar ridge give origin to brachioradialis whereas the lower one third gives rise to extensor carpi radialis longus.
The anteromedial surface, near the lower end of the medial supracondylar ridge, gives origin to the humeral head of pronator teres. {The other end arises from ulna on the medial side of the coronoid}
The common flexor origin on the anterior aspect of the medial epicondyle gives rise to superficial flexors of wrist and hand, commonly called flexor forearm muscles. These are flexor carpi ulnaris, palmaris longus, flexor carpi radialis and pronator teres
The common extensor origin on lateral epicondyle provides origin to the extensor muscles of the forearm. These muscles are brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorium, extensor digiti minimi, and extensor carpi ulnaris.
The posterior surface of the lateral epicondyle gives rise to the anconeus muscle.
The capsular 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 posteriorly.
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.
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)
