The humerus is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections:
- Proximal humerus
- Distal humerus
The upper or proximal extremity of the humerus consists of the bone’s large rounded head joined to the body by a constricted portion called the neck, and two eminences, the greater and lesser tubercles.
The greater and lesser tubercles are the site of attachment for the four rotator cuff muscles.
Attachments of the Rotator Cuff
The greater tubercle has 3 facets for attachment of the rotator cuff muscles:
- Superior facet: supraspinatus
- Middle facet: infraspinatus
- Inferior facet: teres minor
The subscapularis attaches to the lesser tubercle
Bicipital Groove and Muscle Relations
- Tendon of long head of biceps brachii tendon runs in the bicipital groove
- Lateral lip: pectoralis major attachment
- Floor of groove: teres major
- Medial lip: latissimus dorsi
Shaft of Humerus
The body or shaft of the humerus is triangular to cylindrical in cut section and is compressed anteroposteriorly.
The radial groove is seen on the posterior surface of the upper humerus. The radial nerve and profunda brachii artery run in this groove.
The deltoid tuberosity is seen on the lateral aspect of the humerus providing the attachment for the deltoid muscle
- capitulum: articulates with head of the radius
- trochlea: articulates with the proximal ulnar.
- coronoid fossa: receives the coronoid process of the ulna during flexion of the forearm.
- olecranon fossa: posterior aspect of distal humerus, during forearm extension this fossa accomodates the olecranon.
- radial fossa: receives the anterior border of the head of the radius, when the forearm is flexed.
The epicondyles are continuous above with the supracondylar ridges (lateral and medial supracondylar ridges).
- lateral epicondyle: attachment for the radial collateral ligament and common extensor origin
- medial epicondyle: attachment for the ulnar collateral ligament and common flexor origin. The ulnar nerve runs in a groove on the back of this epicondyle.
Proximal: humerus articulates with the scapula at the glenoid fossa – glenohumeral joint
Distal: Elbow joint formed by the humeroradial (capitellum and radial head) and humeroulnar (trochlea and trochlear notch of the ulnar) articulations.