Epicondylitis

Lateral Epicondylitis

Henry J. Morris first described “lawn tennis elbow,” now referred to as lateral epicondylitis, in 1882 (Figure 1). The annual incidence of lateral epicondylitis is approximately 1% to 3% of the general population, with the majority of patients being 35 to 40 years old or older. Men and women are affected equally. Lateral epicondylitis typically occurs in racquet and throwing sports but can result from work-related injury as well. The etiology is believed to be overuse and repetitive microtrauma from eccentric contractions of the extensor muscles. The injury occurs between the extensor carpi radialis brevis and the periosteum of the lateral epicondyle. A microscopic invasion of immature fibroblast and nonfunctional vascular buds leads to an “angiofibroblastic tendinosis,” first described by Nirschl in 1979. Scarring and calcifications develop within the degenerated tendon, with little to no inflammatory cells present; the term epicondylitis is a misnomer, as “itis” implies the major cause to be an inflammatory process, and anatomical studies do not support this. Studies have shown that this area is extremely hypovascular—that is, it does not receive a generous blood supply—thus limiting its potential to heal.

For proper evaluation and accurate diagnosis, the examiner must have a good understanding of elbow anatomy. The elbow is a hinge joint that can flex, extend, and rotate. The medial trochlea of the distal humerus articulates with the ulna, allowing for flexion and extension. The lateral capitellum of the distal humerus articulates with the radial head. The radiocapitellar and radioulnar articulations allow for rotation of the elbow joint. Valgus stability is provided by the medial collateral ligament complex, comprising the anterior, posterior, and transverse bundles, with the anterior bundle being the primary stabilizer. Rotational and varus stability are provided by the lateral collateral ligament complex, comprising the radial collateral ligament and annular ligament. Elbow flexion is facilitated by the biceps brachii, brachioradialis, and brachialis muscles. The triceps and anconeus allow for elbow extension. The supinator and biceps brachii are the major supinators, while the pronator quadratus, pronator teres, and flexor carpi radialis muscles are the major pronators. The median, ulnar, and radial nerves all traverse the elbow joint, providing sensory and motor innervation. The brachial, radial, and ulnar arteries are the major vessels of the elbow.

Figure 1 Tennis Elbow (Lateral Humeral Epicondylitis)

Patients with lateral epicondylitis often complain of weak grip and pain along the extensor surface of the forearm. Physical exam shows tenderness to palpation along the lateral epicondyle and extensor carpi radialis brevis. Pain is reproducible with resisted wrist extension, resisted supination, and resisted long finger extension.

The majority of cases are diagnosed clinically, but imaging can help if the presentation is less clear. Plain radiographs (X-ray films) are usually normal but may show a calcification [Page 431]around the epicondyle in 20% of patients. Ultrasound is a noninvasive modality increasingly used both for diagnosis and to guide treatment of epicondylitis. Calcifications, tears, or a thickened, degenerative tendon may be seen, and selective injections and/or tendon fenestration may be done under ultrasound guidance. Magnetic resonance imaging (MRI) is the most sensitive imaging technique, but its utility is usually limited to preoperative imaging. Images may reveal tendon thickening, edema, microtears, and fibrovascular proliferation.

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