INTRODUCTION

Although many tissues are subject to fatigue injury, especially those of the immature skeleton,¹⁷ the concept of “overuse syndrome” has a broader definition. “No pain, no gain,” a cliché promoted in athletic circles for decades, expresses the underlying attitude that the advancement of one’s physical abilities may depend on exceeding the body’s limits far enough to cause pain and that less vigorous activity constitutes suboptimal performance. The pain that results from these activities may be transient, representing little more than a focal accumulation of muscle metabolic byproducts, or it may be longer lasting, indicating tissue injury. One dilemma is where to draw the line between the two extremes. Others are when it is safe to resume the activities that initially led to the noxious episode, whether or not adjustments in those activities are indicated, and at what point persistent pain no longer represents an acute injury state but signals a more ominous and less understood condition of chronic pain. These are only a few of the unknowns that are associated with overuse syndromes.

DEFINITIONS AND SYNONYMS

Usually thought to affect muscle or nerve, the overuse syndromes are imprecisely defined and go by a variety of names—repetitive strain injury, repetitive stress syndrome, chronic pain syndrome, cumulative trauma disorder, pain dysfunction syndrome (see Chapter 81), cervicobrachial occupational disorder, fibromyalgia, and a variety of activity-specific conditions such as writer’s cramp and tennis elbow, among others.^{6,12,16,18,33,40} The multiplicity of terms reflects the fact that the pathophysiologic mechanisms are, at best, poorly understood. It also contributes to confusion in classification, which, in turn, interferes with our learning from outcome studies. Overall, however, the term overuse syndrome is generally understood to reflect a painful condition, and all tissue types are at risk (Table 50-1). In this text, the term applies to a painful condition of the elbow region that results from excessive activity and whose symptoms have been present for an extended period of time.¹⁵

TABLE 50-1 Overuse-Induced Lesions at the Elbow and Affected Tissue Types

Overuse syndrome is a diagnosis of exclusion. No clear history of injury or date of onset is reported. Conditions that involve injury to specific structures, such as lateral epicondylitis and nerve entrapment syndromes (discussed in other chapters), must be ruled out before overuse conditions are considered. Chronicity also plays a role in the diagnosis of overuse syndrome. Pain of traceable onset less than 3 months before presentation for evaluation may be more likely to signify actual tissue injury related to a specific set of circumstances and to respond more favorably to conventional medical intervention. Conversely, pain of more than 6 months’ duration is much more likely (1) to have been affected by numerous nonorganic factors, (2) to present as a regional complaint, and (3) to display resistance to conventional medical intervention.⁶

EPIDEMIOLOGY

The overuse syndromes are most prominent in two groups of patients, performers and workers.^{5,7,8,11,15,20,27,36,39} Among the former are athletes and musicians, whose professions demand exceptional physical performance and arduous practice sessions. The tissues most often involved in athletes are the musculotendinous units, the ulnar nerve, and the collateral ligaments.³⁸ In practice sessions, an activity is repeated to improve the performance level, often for extended periods. When the performers are called on to use the skills so perfected, an alteration in the performance level caused by pain may be noticeable and possibly may threaten their ability to continue. Any pre-existing injury can further increase the risk of developing an overuse condition.

Workers who daily are expected to perform certain job tasks are also at risk. Occupations reported to carry increased risk for overuse syndromes include typist, telephone operator, cash register operator, interpreter for the deaf, and packing plant worker.^8,14,19,33 In the most common scenario, workers are stationed for long periods, during which they perform repetitive tasks. The actual number of workers who suffer from overuse syndrome is difficult to determine. Four percent of noninstitutionalized adults could recall at least 1 month of musculoskeletal pain and the nature of the impact of that pain.⁹ When specific jobs are evaluated, however, the incidence of upper extremity pain related to overuse may approach 30%.²⁹

In both groups, psychosocial influences may play a major role in determining the pattern of functional recovery once a change in performance level is detected. Such factors actually may influence the manner in which the painful condition is presented to the treating physician, which, in turn, may alter the diagnosis and generate a self-perpetuating cycle of pain and reinforcement behaviors. It also must be understood that the worker’s condition is not static and that new stresses may enter into the situation over time. Often, the patience of both employee and employer evaporates and mutual mistrust develops. This may prompt the patient subconsciously to exaggerate reports of pain and limitation of function, further frustrating the care of the condition and often ending in confrontation and litigation.

ETIOLOGY

The causes of overuse syndrome have been the subject of speculation in many publications and studies.^{10,24,31,35,37} One of the earliest observations of pain in a worker subjected to “irregular motions and unnatural postures” dates to the early 18th century.³⁷ Generally, overuse conditions are believed to arise from a combination of static and dynamic loads applied to postural muscles beyond the tolerable contraction level or duration.³¹ Isometric contraction greater than 10% of the maximum contraction level is not recommended³⁵ because circulation in the contracting muscle may be compromised enough to cause tissue ischemia and accumulation of noxious metabolites.²⁴ The noxious stimulus may prompt recruitment of other muscle groups, which, however, may be at a mechanical disadvantage for assuming such a role and may likewise, in the end, suffer muscle strain. The Japanese Association of Industrial Health identified several risk factors for the development of overuse syndrome, including dynamic muscle recruitment for repetitive tasks, static muscle recruitment for postural support, uncomfortable postures, mental stress, and ergonomic factors such as unpleasant working conditions (Fig. 50-1).² Continued engagement in high-load activities other than occupational tasks, including hobbies, domestic chores, and recreational activities, may perpetuate the condition by reducing recovery time.

FIGURE 50-1 A 32-year-old carpenter had pain on elbow motion of 40 to 110 degrees. Primary arthrosis prompted a career change.