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94 m a s s a g e & b o d y w o r k s e p t e m b e r / o c t o b e r 2 0 1 9 technique CLINICAL EXPLORATIONS Current Views on Lateral Epicondylitis By Whitney Lowe 1 One of the most common upper extremity overuse problems is lateral epicondylitis (LE), commonly referred to as tennis elbow. LE affects roughly 1–3 percent of the general population in the United States each year. Despite its common name of tennis elbow, only about five percent of the people with LE developed the condition from playing tennis. 1 The dramatic increase of repetitive motions in numerous occupations has led to a surge of epicondylitis over the last several decades. Due to the nature of our work, LE is a common problem affecting massage therapists. There are also heavy socioeconomic burdens associated with this condition. These burdens include lost productivity for employers, lost or diminished wages for employees, long periods of pain, and significant workers' compensation claims. This article will focus on lateral epicondylitis, but the same principles hold for medial epicondylitis, which is a similar condition affecting the wrist flexor muscles. ANATOMICAL BACKGROUND Lateral epicondylitis affects the common wrist extensor tendon near the elbow. This proximal tendon is a conjoined tendon shared by the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris (Image 1). The main tendon affected in most cases of LE is the extensor carpi radialis brevis (ECRB). It's not immediately clear why this tendon is affected more than the others, except that its anatomical arrangement and line of pull are likely putting the greatest load on this portion of the tendon. This common tendon inserts into the lateral epicondyle of the humerus. When the tendon is overused, tenderness can be felt in the tendon, as well as where the tendon blends into the periosteum of the bone. The periosteum is a thin membrane covering the bone and is one of the most pain-sensitive tissues in the body. That is one reason why constant pulling from an overused tendon produces pain at the tendon attachment site. The extensor carpi radialis brevis and other common wrist extensor tendons at the lateral epicondyle. Image from 3D4Medical's Complete Anatomy application. Common extensor tendons ECRB THE PATHOLOGY LE is most commonly associated with repetitive overuse actions of the wrist extensor muscles. These actions could include repetitive or forceful wrist extension, long periods of gripping objects, or movements that include forearm supination or radial deviation. Repetitive eccentric loading on the wrist extensors is also a primary cause. A repetitive eccentric load would be one where the wrist extensors are trying to prevent the wrist from moving into flexion while slowly resisting that motion (Image 2). In addition to repetitive motion, long periods of isometric contraction of the wrist extensors may also lead to LE. For example, grasping tools or implements during occupational activities might not involve repetitive motion as much as constant contraction to hold the implement in