Applied Anatomy

The elbow joint acts as both a hinge and a swivel, providing a stable link for lifting, pushing, or gripping and for positioning the hand in space. The hinge is formed by the humeroulnar (trochleoulnar) and humeroradial (capitelloradial) articulations at the cubital joint. The trochleoulnar is the principal joint, and the swivel is formed by the proximal radioulnar joint. These three joints share a common synovial cavity (Figure 3-1A).

FIGURE 3-1 A & B, BONES AND MUSCLES OF THE ELBOW.

Stability of the elbow depends upon congruity of the articulating bones, anterior capsule, ligaments, and surrounding muscles. The ulnar and radial collateral ligaments provide medial and lateral stability to the joint. The cup-shaped annular ligament encircles the radial head and holds it in the radial notch of the proximal ulna (Figure 3-2A, B).

FIGURE 3-2 A & B, LIGAMENTS OF THE ELBOW.

The common flexor tendon of the elbow (pronator teres, flexor carpi radialis, palmaris longus, flexor digitorum superficialis, and flexor carpi ulnaris) takes origin from the medial epicondyle and supracondylar ridge of the humerus. The common extensor tendon (extensor carpi radialis longus and brevis, brachioradialis, extensor digitorum communis, extensor carpi ulnaris, and anconeus) originates from the lateral epicondyle, supracondylar ridge, and distal humerus. The biceps tendon crosses the elbow joint to insert into the radial tuberosity (see Figure 3-1B).

The ulnar nerve runs in a bony groove behind the medial epicondyle (the cubital tunnel; Figure 3-2A). The olecranon bursa, a subcutaneous cushion at the olecranon process, is synovially lined but is anatomically separate from the elbow joint (see Figure 3-2B).

Full elbow extension, the neutral (anatomic) position, is defined as 0° (not 180°). Some normal men, particularly muscular men, may lack 5° to 10° of full extension; normal women may demonstrate up to 10° of hyperextension.

With the elbow in full extension, there is normally a slight valgus angulation of the forearm with respect to the humerus. This angulation, referred to as the carrying angle, is due to the oblique shape of the trochlea (see Figure 3-1A) and is normally ~5° to 10° in men and ~10° to 25° in women (Figure 3-3). This angle allows the forearms to clear the hips during the normal arm swing of ambulation and is important for carrying objects at the side, without requiring shoulder abduction. Excessive deviation of the forearm away from the body is referred to as cubitus valgus, and deviation of the forearm toward the body is called cubitus varus.

FIGURE 3-3 CARRYING ANGLE.

A, Right arm: normal; left arm: varus. B, Right arm: normal; left arm: valgus.

Normal elbow flexion is from 0° to 160°. Any deficit in full extension is referred to as a flexion contracture (joint contracture in the direction of flexion). The brachialis, biceps, and brachioradialis are the primary flexors of the elbow, and the large, powerful triceps and small, relatively weak anconeus are the extensors. A minimum total arc of elbow flexion–extension of ~100° is required for normal activities.

Pronation of the forearm and hand (palm of hand facing posteriorly in anatomic position) and supination (palm facing anteriorly in anatomic position) occur at the proximal and distal radioulnar joints, as the radial head pivots on the capitellum while the distal radius rotates around the distal ulna (see Figure 3-3). Normal pronation is ~75° and supination is ~85°. The pronator teres and pronator quadratus are the principal pronators, and the biceps and supinator muscles are the primary supinators of the radioulnar joints. A minimum total arc of pronation–supination of ~100° is required for normal activities.

History

Elbow pain is commonly caused by a relatively small number of conditions that include periarticular (tendinitis and bursitis), articular (arthritis), bone (fracture and dislocation), or neurologic problems (Table 3-1).

TABLE 3-1 COMMON CAUSES OF ELBOW PAIN

Evaluation of elbow pain focuses on answering three important questions: 1) Is there evidence of major trauma or injury? 2) Can symptoms and signs be adequately explained by a local problem confined to the elbow? 3) Is there evidence of a more generalized articular process, of which the elbow is only a part, or a neurologic process with elbow symptoms referred from another site?

Assessment of elbow pain requires a careful delineation of pain characteristics and associated features. A helpful mnemonic for characterizing pain in almost any site is OPQRST: O = onset, P = precipitating (and ameliorating) factors, Q = quality, R = radiation, S = severity, and T = timing.

An initial screening history should readily identify those patients with elbow pain secondary to fracture or dislocation, and an appropriate radiographic and orthopedic assessment can be initiated. A history of unusually intense or repetitive recreational or occupational activity is important, particularly in patients with suspected tendinitis. Furthermore, pain characteristics may suggest neurologic involvement (burning, tingling, and radiation), and associated symptoms in the neck and shoulder or wrist and hand may suggest pain referral from a site other than the elbow. Additional articular symptoms in other sites may suggest a more generalized process, such as rheumatoid or psoriatic arthritis.

Physical Examination