Humerus

Head

The head is a hemispheroidal shape, with hyaline cartilage covering its smooth articular surface. In the anatomical position, the head faces in a medial, superior and posterior direction where it articulates with the glenoid fossa of the scapula.

Anatomical neck

The anatomical neck is a slight narrowing below the articular surface of the head. Here, the joint capsule of the shoulder joint is attached.

Greater tubercle

The greater tubercle is the most lateral portion of the proximal end of the humerus. It consists of three smooth and flat impressions at the posterosuperior aspect for the attachment of muscles. From superior to inferior, the muscles that attach at these impressions are the:

• supraspinatus
• infraspinatus
• teres minor 

Remember the muscles attaching to the greater tubercle of the humerus using the following mnemonic!

Sally and Ingrid Teach Maths

• Supraspinatus
• Infraspinatus
• Teres Minor

The deltoid muscle covers the lateral aspect of the greater tubercle, resulting in the normal rounded shape of the shoulder. The lateral aspect also contains multiple vascular foramina.

Lesser tubercle

The lesser tubercle is located anterior to the anatomical neck and has a smooth, palpable muscular impression. The lateral part forms the medial margin of the intertubercular sulcus. The subscapularis muscle attaches at this tubercle and the transverse ligament of the shoulder also attaches on its lateral part.

Intertubercular sulcus

The intertubercular sulcus is an indentation located between the two tubercles. It is sometimes referred to as the bicipital groove. The long tendon of the biceps brachii and an ascending branch of the anterior circumflex humeral artery are located within the sulcus. The sulcus consists of a lateral lip and a medial lip. The tendon of the pectoralis major muscle attaches on to the lateral lip (a.k.a. crest of greater tubercle), while the teres major tendon attaches on to the medial lip. In addition, the tendon of lattisimus dorsi attaches to the posterior aspect.

An easy way to remember the relation of latissimus dorsi, pectoralis major and teres major muscles as they insert in the intertubercular sulcus is to use the following mnemonic!

'Lady between two majors'

• Lady: Latissimus dorsi
• Majors: Teres Major, pectoralis Major

Surgical neck

There is also a narrowing below the tubercles referred to as the surgical neck, which is a common fracture site.

It is in close proximity to the axillary nerve and the posterior circumflex humeral artery. This is where the proximal end of the humerus joins with the long shaft.

Borders

The anterior border begins at the greater tubercle and runs downward almost to the end of the bone. The proximal end of the anterior border is continuous with the lateral lip of the intertubercular sulcus.

The lateral border begins just distal to the greater tubercle of the humerus. It thickens distally to form the lateral supracondylar ridge. The middle portion of the lateral border is adjacent to the rough V shaped area referred to as the deltoid tuberosity.

The medial border is similar to the lateral border in that it forms the medial supracondylar ridge distally. The radial groove is a shallow groove that interrupts the lateral border in its medial third. The radial nerve and deep brachial artery are located in this groove.

How well do you know the other 205 bones in the body? Test your knowledge with our bone quizzes and labeled diagrams.

Surfaces

The anterolateral surface is an area limited between the anterior and lateral borders. It has a smooth proximal surface and is largely covered by the deltoid muscle. The deltoid inserts into the deltoid tuberosity around the middle of the surface. The lateral portion of the brachialis muscle originates from the distal part of this surface, as well as from the proximal two third of the lateral supracondylar ridge. 

The anteromedial surface is located between the anterior and medial borders of the shaft/body, beginning proximally at the floor of the intertubercular sulcus. It provides attachment for the coracobrachialis muscle around its mid-portion, while the distal half of the surface is largely covered by the medial portion of the brachialis muscle.

The posterior surface is bounded by the medial and lateral borders and is covered mostly by the medial head of the triceps brachii muscle. A ridge on the proximal third also gives attachment to the lateral head of the triceps brachii.

Trochlea

The trochlea has a surface shaped like a pulley and covers the anterior, posterior and inferior surfaces of the medial condyle of the humerus. It articulates with the ulna at the trochlear notch.

When the elbow is in the extended position, the posterior and inferior aspects of the trochlea are in contact with the ulna. However, when the elbow is flexed the posterior part is no longer in contact, as the trochlear notch slides towards the anterior aspect of the humerus.

Capitulum

The capitulum is a convex and rounded projection that covers the anterior and inferior surfaces of the lateral condyle of the humerus.

Unlike the trochlea, it doesn’t cover the posterior surface. It articulates with the head of the radius. In extension, the inferior surface is in contact with the radius but in the flexed position the radial head slides towards the anterior aspect of the humerus.

Differentiate between the trochlea and capitulum at the elbow joint very easily using this mnemonic!

CRAzy TULips

• Capitulum = RAdius
• Trochlear = ULnar

Medial epicondyle

The medial epicondyle is a blunt projection superomedial to the medial condyle, which forms at the end of the medial border of the humerus. The ulnar nerve crosses its smooth posterior surface and is palpable in this location. The superficial muscles of the anterior compartment of the forearm originate from the anterior surface of the medial epicondyle. These muscles are the:

• flexor carpi ulnaris
• palmaris longus
• flexor carpi radialis
• pronator teres

Sometimes it can be difficult to remember if the common flexor tendon is medial or lateral. Here's a mnemonic that can help you out.

FM radio

• Flexor Medial, so Common Flexor origin is on the medial side

Lateral epicondyle

The lateral border of the humerus ends at the lateral epicondyle. There is an impression on the lateral and anterior surfaces where the seven muscles of the superficial group of the posterior compartment of the forearm originate. These include the:

• brachioradialis
• extensor carpi radialis longus
• extensor carpi radialis brevis
• extensor digitorium
• extensor digiti minimi
• extensor carpi ulnaris
• anconeus

Olecranon fossa

The olecranon fossa is a deep hollowed area on the posterior surface, superior to the trochlea. In elbow extension, the tip of the ulnar olecranon process lodges into this fossa.

Coronoid fossa

The coronoid fossa is a smaller hollow that is also located superior to the trochlea, but on the anterior surface. During flexion of the elbow, the coronoid process of the ulna lodges into the coronoid fossa. Lateral to the coronoid fossa and superior to the capitulum is another depression referred to as the radial fossa. It is so named as the margin of the head of the radius lodges there in full flexion.

Learn everything about the humerus anatomy here:

Mnemonic

There are quite a lot of anatomical features at the distal end of the humerus, don't you think? Remember them more easily using the following mnemonic!

'CITE two Freaks'

• Capitulum
• Internal (medial) epicondyle
• Trochlea
• External (lateral) epicondyle
• Olecranon and coronoid Fossae

Don't forget to check out our quiz on the structures of the humerus and scapula!