The elbow is the anatomic junction between the arm and forearm. Whereas the shoulder functions to place the upper extremity anywhere within the wide sphere of its range of motion, the elbow functions to adjust the extremity's height and length and the functional position of the hand to accomplish prehensile tasks efficiently. The elbow's three separate synovial articulations housed within one joint capsule present unique challenges to clinicians involved in treating trauma and dysfunction at this joint.
The bones of the elbow are the distal humerus, the proximal ulna, and the proximal radius (Fig. 16-1). The articulation between the humerus and ulna is the humeroulnar joint. The articulation between the humerus and radius is the humeroradial joint. The articulation between the proximal portions of the ulna and radius is the proximal radioulnar joint. These three separate articulations are within a common joint capsule and together make up the elbow joint.
Osseous anatomy of the elbow: (A) anterior aspect (left elbow), (B) lateral aspect (right elbow).
The humeral shaft expands at its distal end into medial and lateral humeral condyles. The articular portions of these condyles are the trochlea and capitulum. The spool-shaped trochlea is divided by a semicircular groove or trochlear sulcus. The trochlea is on the medial aspect of the distal humerus and articulates with the ulna. The rounded capitulum, also called the capitellum, is on the lateral aspect and articulates with the radius. The medial and lateral epicondyles are projections located proximally to the trochlea and capitulum, respectively. The distal humerus is marked by three depressions or fossae. Anteriorly, the coronoid fossa and radial fossa receive the ulnar coronoid process and radial head at full elbow flexion. Posteriorly, the olecranon fossa receives the ulnar olecranon process at elbow extension.
The proximal ulna has two beaklike processes: the large olecranon process at its proximal end and the coronoid process on its anterior surface. Between these two processes lies the articular concave trochlear notch, which receives the trochlea. The shallow radial notch on the lateral side of the ulna articulates with the radial head.
The proximal radius is distinguished by a head, a neck, and a tuberosity. The radial head is disklike and cupped on its upper end, articulating with the capitulum above and the ulna medially. The neck is the constricted area below the head, and the tuberosity is an oval prominence distal to the neck.
The radial and ulnar bones together are referred to ...