Upper Extremity Musculoskeletal Disorders: Occupational Association and a Model for Prevention

John C. Rosecrance and Thomas M. Cook

Corresponding author: John C. Rosecrance, PT, Ph.D.
Department of Preventive Medicine and Environmental Health
The University of Iowa
156 I.R.E.H. – Oakdale Campus
Iowa City, IA 52242-5000
Tel: 319-335-4554
FAX: 319-335-4225

CEJOEM 1998; 4(3):214-231

Key Words:
ergonomics, musculoskeletal disorders, occupational disease, prevention

CTS – carpal tunnel syndrome
MSDs – musculoskeletal disorders

The authors review evidence associating job tasks to various musculoskeletal disorders (MSDs) in the workplace and discuss a model for the prevention of these disorders. Despite the abundant literature, the causal relationships between MSDs and occupationally related factors remain the subject of considerable debate. The prevalence of occupationally related MSDs has increased dramatically in developed and developing countries. Several work-related risk factors such as awkward postures, high repetition rates, and/or forceful exertions have been associated with the increased prevalence of MSDs. It is likely many MSDs reported in the workplace have a multi-factorial etiology with psychosocial and individual factors contributing. Health and safety programs emphasizing primary prevention strategies have been proposed to reduce the prevalence of MSDs. Prevention of MSDs can lead to significant reductions in occupational disorders, decreased health care costs, and improvements in production efficiency.


Musculoskeletal disorders were recognized as having an occupational related etiology as early as the beginning of the 18th century. In 1713, Bernardini Ramazzini, the father of occupational medicine, in his treatise De Morbis Artificum Diatriba (“Diseases of Workers” as translated by Wright, 1940) documented that musculoskeletal disorders were associated with workplace factors. Regarding bakers, Ramazzini noted, “Now and again, I have noticed bakers with swelled hands, and painful too; in fact the hands of all such workers become much thickened by the constant pressure of kneading the dough” (Wright 1940). Of sedentary workers, Ramazzini observed, “men and women who sit while they work at their jobs, become bent, hump-backed and hold their heads like people looking for something on the ground; this is the effect of their sedentary life and the bent posture as they sit …” (Wright 1940).

It was not until the 1970s that occupational factors were examined using epidemiologic methods, and the issue of work-relatedness of these conditions began appearing regularly in the international scientific literature. Since then, the literature has increased dramatically with more than 6,000 published scientific articles addressing musculoskeletal disorders (MSDs) and ergonomics in the workplace (NIOSH 1997). Despite the abundant literature, the causal relationships between MSDs and work-related factors remain the subject of considerable debate. Researchers in Australia, Asia, Scandinavia, Western and Central European countries, South America, and North America have been actively studying these relationships in an effort to prevent and reduce MSDs in working populations (Hagberg et al. 1992, Kákosy 1994, Kilbom et al. 1986, Leclerc et al. 1998, Lusa-Moser et al. 1997, Maeda et al. 1982, Muruka 1997, Ohlsson et al. 1995, Pórszász et al. 1997, Silverstein et al. 1987, Yu and Wong 1996). Musculoskeletal disorders are thought to be a major cause of lost time from work and worker disability. Worker compensation claims and health care costs for MSDs has risen rapidly over the last decade in most industrialized countries (Stock 1991).

The World Health Organization has characterized “work-related” diseases as multi-factorial to indicate that a number of risk factors (e.g., physical, work organizational, psychosocial, individual, and sociocultural) contribute to causing these diseases (WHO 1985). There is disagreement, however, on the relative importance of occupational and individual factors in the development of work-related illnesses. The same controversy has been an issue with other medical conditions (occupational and non-occupational) such as certain cancers and lung disorders, both of which have multiple causality. The purpose of this paper is to present an overview of the epidemiologic evidence on the relationship between upper extremity MSDs and workplace factors, and to outline a model for the prevention of these disorders.

Scope and Magnitude of the Problem

Although occupational MSDs have been reported in the literature since the 18th century it was not until the mid 1980s that Australia, New Zealand, and several European countries documented significant outbreaks of occupational MSDs and compensable complaints (Young et al. 1992). Later, in the early 1990s, a similar increase in MSDs was detected in the United States and to a slightly lesser extent in the United Kingdom. As the rate of compensable claims increased, work-related MSDs were finally recognized as a problem with enormous human and economic ramifications. While no global figures exist, data concerning occupational MSDs are largely determined from national sources, the majority of which are from industrialized countries.

In the United States, the only routinely published national source of information about occupational injuries and illnesses is the Annual Survey of Occupational Injuries and Illnesses conducted by the Bureau of Labor Statistics (BLS) of the United States Department of Labor. This survey is a random sample of about 250,000 private-sector enterprises, but it excludes self-employed workers, farms with fewer than 11 employees, private households, and all government agencies. The Annual Survey of Occupational Injuries and Illnesses data provides estimates of workplace injuries and illnesses from information that employers provide to the Department of Labor from their log of recordable injuries and illnesses. In recent years, the majority (approximately 65%) of the illnesses have been due to repetitive trauma of the upper extremities (BLS, 1997). The number of repetitive trauma cases has increased dramatically, rising steadily from 23,800 in 1972 to 332,000 in 1994–a 14-fold increase (Figure 1). The number of cases decreased by 7% and then again by another 9% in 1995 and 1996, respectively. In the United States, all back disorders are categorized separately into a single, broad “injury” category rather than as an illness and are not included in these numbers.

Figure 1. Disorders Associated with Repeated Trauma in the United States from 1980 to 1996.

Cost of MSDs in the United States

The precise costs of occupational MSDs are not easily defined. Estimates of the economic burden associated with occupational MSDs vary depending on which costs are used in the calculations. A conservative estimate previously published by NIOSH for the workers’ compensation costs in the United States related to low back and upper extremity MSDs is USD $13 billion annually (NIOSH 1996). Webster and Snook (1994) estimated that the mean compensation cost per case of upper-extremity, work-related MSD was USD $8,070 in 1993. The California Workers’ Compensation Institute (a non-profit research institute) estimates that upper-extremity MSD claims by workers averages USD $21,453 each (CWCI 1993). The compensable cost is limited to the medical expenses and indemnity costs (lost wages). When other expenses such as the full lost wages, lost production, cost of recruiting and training replacement workers, cost of rehabilitating the affected workers, etc. are considered, the total cost to a nation’s economy becomes much greater.

Definition of MSD, RSI, OCD, CTD, WMD

Musculoskeletal disorders or MSDs usually involve repeated trauma to muscles, tendons, and peripheral nerves and are given various names depending upon the country of origin. In Australia, the term repetitive strain injury (RSI) refers to “… a soft tissue disorder caused by overloading of particular muscle groups from repetitive use of constrained postures” (National Occupational Health and Safety Commission 1985). In Japan the concept of occupational cervicobrachial disorder (OCD) has been adopted (Maeda et al. 1977, Maeda et al. 1982). OCD is defined as “functional and/or organic disturbance resulting from doing jobs in a fixed position with repetitive movement of the upper extremities,” and as being of occupational origin (Maeda et al. 1982). The term cumulative trauma disorders, or CTDs, is common in North America and can be defined as the adverse health effects that arise from chronic exposure to microtrauma (Putz-Anderson 1988). To include an occupational component, the phrase “work-related musculoskeletal disorder (WMD)” has recently been coined.

Not specific to any one type of job, MSDs tend to affect workers in a wide variety of occupations ranging from construction work, assembly line tasks and meat processing jobs, to computer use by newspaper editors. Occupational MSDs usually take months or even years to develop. Thus, it can be difficult to associate specific exposure to defined outcomes. The most common health outcome in the quantification of MSDs has been the occurrence of pain, which is assumed to be the precursor of more severe disease (Riihimaki 1995). Different epidemiologic measures and time scales have been used to quantify MSDs and often include measures of lifetime prevalence, period prevalence, point prevalence, and incidence ratios. Cross-sectional studies usually employ case definitions that take into account prevalent cases at different stages of the disease process. Because of the multi-factorial nature of MSDs, it has been necessary to look at a broad spectrum of outcome measures to assess the effects of these factors.

Even within a geographical region, the definition of a musculoskeletal disorder (or similar term) often varies depending on the study. Thus, it is not surprising that controversy has arisen regarding the relative importance of various risk factors in the etiology of these disorders. Some investigators restrict themselves to case definitions based on clinical pathology, some to the presence of symptoms, some to “objectively” demonstrable pathological processes (e.g., nerve conduction abnormalities), and some to work disability (e.g., lost work-time status). Although occupational MSDs range from eyestrain to low back pain, common upper extremity conditions include: carpal tunnel syndrome, wrist tendinitis, epicondylitis at the elbow, shoulder bursitis and tendinitis, and myositis in the neck region.


Carpal Tunnel Syndrome

One of the most highly publicized occupationally-related MSDs is carpal tunnel syndrome (CTS). CTS can be a disabling condition that gradually progresses from an onset of tingling and numbness in the fingers to pain, clumsiness, and muscle atrophy of the hand. In recent years, the literature relating occupational factors to the development of CTS has been extensively reviewed by numerous authors (Armstrong et al. 1993, Gerr et al. 1991, Hagberg et al. 1992, Kuorinka and Forcier 1995, Moore 1992, Stock 1991, Viikari-Juntura 1995). Most of these reviews have concluded that work factors are one of the important causes of CTS. According to a NIOSH review of 30 studies on the occupational factors associated with CTS, “there is strong evidence of a positive association between exposure to a combination of occupational risk factors (e.g., force and repetition, force and posture) and CTS” (NIOSH 1997). Additionally, the review indicated that there is evidence of a positive association between CTS and either work-related repetition or force alone.

There are several studies that have investigated the specific relationship between tasks involving repetition and force and CTS (Chiang et al. 1993, Moore and Garg 1994, Roquelaure et al. 1997, Silverstein et al. 1987). Silverstein et al. (1987) studied 652 workers in 39 jobs from 7 different plants (electronics, appliance, apparel, and bearing manufacturing; metal casting, and an iron foundry). Investigators classified jobs into 4 groups that accounted for force and repetitiveness: low force/low repetitiveness, high force/low repetitiveness, low force/high repetitiveness, and high force/high repetitiveness. Fourteen cases of CTS were diagnosed based on standardized physical examinations and structured interviews.). There was a statistically significant association between CTS and highly repetitive jobs compared to low repetitive jobs, irrespective of force. Force alone was not statistically associated with CTS. Using multiple logistic analysis a statistically significant odds ratio of 15.5 was computed for jobs with combined exposures to high force and high repetition compared to jobs with low force and low repetition. Age, gender, plant, years on the job, hormonal status, prior health history, and recreational activities were analyzed and determined not to confound the associations.

Chiang et al. (1993) studied 207 workers from 8 fish processing factories in Taiwan. Jobs were divided into 3 groups based on levels of repetitiveness and force. The comparison group (low force/low repetitiveness) was comprised of managers, office staff, and skilled craftsmen (group 1). Fish-processing workers were divided into high repetitiveness or high force (group 2), and high force and high repetitiveness (group 3). CTS was defined on the basis of symptoms and positive physical examination findings, ruling out systemic diseases and injury. CTS prevalence for the overall study group was 14.5%. CTS prevalence increased from group 1, to group 2, and to group 3 (8.2%, 15.3%, and 28.6%, respectively), a statistically significant trend (p<0.01). Although force significantly predicted CTS, repetitiveness did not. Two significant predictors of CTS in female workers were oral contraceptive use and high force work.

In a recent case-control study of French assembly workers, Roquelaure et al. (1997) evaluated non-occupational and occupational factors associated with CTS. Of the 65 cases identified, 55 had been treated surgically. Referents were randomly selected from the same population. The medical history and household activities of the workers and the ergonomic and organizational characteristics of the job were analyzed. Worksite analysis was performed by direct observation, the use of checklists, and by measuring the weight of tools and parts handled. Exertion of force was statistically associated with CTS (odds ratio 9.0). The only personal factor statistically associated with CTS was a parity of at least 3 (odds ratio 3.2). The authors concluded that the number of risk factors accumulated by the workers was a major determinant of CTS.

Moore and Garg (1994) evaluated 32 jobs in an American pork processing plant and then reviewed past plant medical records for CTS cases in these job categories. Exposure assessment included videotape analysis of job tasks for repetitiveness and awkward postures. The force measure was an estimate of the percent maximum voluntary contraction, based on weight of tools and parts and population strength data, adjusted for extreme posture or speed. Jobs were then predicted to be either hazardous or safe, based on exposure data and judgment. The proportion of CTS in the overall study group during the 20 months of case ascertainment was 17.5 per 100 full time equivalents. The hazardous jobs had a significantly higher relative risk for CTS compared to the safe jobs. The authors concluded that the study provided additional epidemiological evidence that upper extremity musculotendinous disorders and some cases of CTS may be causally associated with working tasks.

The relationship between vibration and CTS has been examined in several studies (Bovenzi 1994, Chatterjee 1992, Silverstein et al. 1987). In a study of Italian stone workers Bovenzi (1994) compared 145 quarry drillers and 425 stone carvers exposed to hand vibration to 258 polishers and machine operators who performed manual activity without exposure to hand-transmitted vibration. CTS was assessed by a physician, and exposure was assessed through direct observation of vibrating tools and by interview. Vibration was also measured in a sample of tools. The vibration-exposed stone cutters had a statistically significant odds ratio of 3.4 for CTS relative to the non-exposed group controlling for several confounders. Other studies have associated peripheral neuropathies in the throacic outlet and cubital tunnel with workers exposed to hand and arm vibration (Kákosy 1994).

Hand/Wrist Tendinitis

Several epidemiologic studies have examined physical workplace factors and their relationship to hand/wrist tendinitis (Amano et al. 1988, Armstrong et al. 1987, Bystrom et al. 1995, Kuorinka and Koskinen 1979, Kurppa et al. 1991, Luopajarvi et al. 1979, McCormack et al. 1990, Roto and Kivi 1984). These studies generally involved populations exposed to a combination of work place risk factors. Overall, however, these studies demonstrate evidence of an association between single factors such as repetition, force, and posture and hand/wrist tendinitis.

Luopajarvi and associates (1979) compared the prevalence of hand/wrist tendinitis among 152 female Finnish assembly line packers in a food production factory to 133 female shop assistants in a department store. Exposure to repetitive work, awkward hand/arm postures, and static work were assessed by observation and videotape analysis of factory workers. The health assessment consisted of interviews and physical examinations conducted by a physiotherapist (active and passive motions, grip-strength testing, observation, and palpation). Diagnoses of tenosynovitis and peritendinitis were later determined by medical specialists using these findings and predetermined criteria. The authors determined that the prevalence rate for tendinitis among the assembly line packers was significantly higher than shop assistants.

Kuorinka and Koskinen (1979) studied occupational rheumatic diseases and upper limb strain among 93 Finnish scissors makers and compared them to the same group of department store assistants (n=143) that Luopajarvi et al (1979) used as a comparison group. Exposure assessment included videotape analysis of scissors maker tasks. The time spent in deviated wrist postures per work cycle was multiplied by the number of pieces handled per hour and the number of hours worked to create a workload index. Diagnoses of tenosynovitis and peritendinitis were determined using predetermined criteria (localized tenderness and pain during movement, low-grip force, swelling of wrist tendons). The prevalence rate ratio for muscle-tendon syndrome among the scissors makers was 1.38 compared to the department store assistants. The study group was 99% female. No association was found between age or body-mass index and diagnoses of muscle or tendon syndromes. The number of symptoms increased with the number of parts handled per year. A non-significant trend of increasing prevalence of diagnosed muscle-tendon syndrome with increasing number of pieces handled per year was noted in a nested case-control analysis.

In Japan, Amano and colleagues (1988) conducted a study to investigate cervicobrachial disorders and other MSDs in shoe factory workers. Finger flexor tenosynovitis was reported among 102 assembly line workers in an athletic shoe factory and 102 age and gender-matched non-assembly line workers. Exposure assessment was based on videotape analysis of the tasks of 29 workers on one assembly line. No formal exposure assessment of the comparison group was reported. Diagnoses were determined by physical examination, including palpation for tenderness. The prevalence rates for tenosynovitis among the shoe factory workers were significantly higher than the non-factory workers. Shoe assembly workers held shoe lasts longer in the left hand and had greater frequency of symptoms in the left upper extremity.


There are fewer epidemiologic studies addressing workplace risk factors for elbow MSDs than for other anatomical regions. Most studies evaluating the workplace for elbow MSDs address the prevalence and risk factor associated with epicondylitis. Epicondylitis is a disorder with an overall prevalence in the general population from 1% to 5% (Allender 1974). Moore and Garg (1994) carried out a medical records review using an epicondylitis case definition based on symptoms and physical examination and an ergonomic assessment of 32 jobs at a meatpacking plant. The authors used a Strain Index to categorize jobs as “hazardous” or “safe” based on observation, video analysis, and judgement of force, posture, repetition and grasp. Using the Strain Index, Moore and Garg (1994) found a significant relationship between hazardous jobs and upper extremity MSDs (of which epicondylitis was a component). The authors reported a significant odds ratio for a case of epicondylitis to occur in a hazardous job.

In a cross-sectional investigation, Punnett et al. (1985) investigated the prevalence of soft tissue disorders of the hands and arms of female garment workers. The findings were compared with the prevalence of disorders in a group of female hospital employees not required to use repetitive hand motion. One hundred and eighty-eight garment workers and 76 hospital employees were surveyed by questionnaire and physical examination. Workers in hand sewing and trimming had high prevalences of persistent pain in all upper limb sites. Stichers had elevated rates of pain in the shoulders, wrists, and hands. Workers ironing by hand had a significant elevation in elbow pain rates. The authors found a significant prevalence rate ratio of persistent elbow symptoms among garment workers performing repetitive and forceful work compared to hospital employees.

Based on a review of 20 epidemiologic studies that examined physical workplace factors and their relationship to epicondylitis, NIOSH (1997) reported that there is insufficient evidence for support of an association between repetitive work or postural factors alone and elbow MSDs. They did, however, determine that there is “some” evidence for an association with forceful work and epicondylitis and strong evidence for a relationship between exposure to a combination of risk factors (e.g., force and repetition, force and posture) and epicondylitis.


Studies from the United States have generally classified shoulder disorders separately from neck disorders when evaluating work-related risk factors. Scandinavian studies examining work-related factors, on the other hand, have often combined neck and shoulder MSDs into one health outcome variable. This is based on the concept that several muscles act on both the shoulder and the upper spine together.

Several studies have reported significant associations between postural variables and neck MSDs (Jonsson et al. 1988, Kilbom et al. 1986, Kilbom and Persson 1987). Kilbom et al. (1986), in a study of electronic workers, reported two significant findings: (1) the more dynamic the working technique, the fewer neck symptoms experienced by electronic workers; and (2) the greater the average time per work cycle spent in neck flexion, the greater the association with symptoms in the neck and neck/shoulder area. A statistically significant association was also obtained from the job analysis variables describing neck forward flexion and upper arm elevation and neck and neck/shoulder disorders.

Shoulder MSDs and their relationship to work risk factors have been reviewed by several authors (Chiang et al. 1993, Hagberg and Wegman 1987, Kuorinka and Forcier 1995, Sommerich et al. 1993). Hagberg and Wegman (1987) attributed a majority of shoulder problems occurring in a variety of occupations to workplace exposure. Kuorinka and Forcier (1995) looked specifically at shoulder tendinitis and stated that the epidemiologic literature is “most convincing” regarding work-relatedness, especially showing an increased risk resulting from overhead and repetitive work.

In a study of fish processing workers in Taiwan, Chiang et al. (1993) studied the relationship between workplace factors and shoulder girdle pain. Shoulder girdle pain was defined as self-assessed symptoms of pain in the neck, shoulder or upper arms, and signs of muscle tender points or palpable hardenings upon physical examination. The force requirements of the jobs were estimated by surface electromyographs in the forearm flexor muscles. Exposure outcome was based on both force and repetitiveness. Using multiple logistic regression analysis with age, gender, and force as co-variates, the authors determined that highly repetitive upper extremity movements were associated with shoulder girdle pain. When tested in the same model with force and repetition, the interaction term for force and repetition was also significant.

In the cross-sectional study by Ohlsson et al. (1995), 85 female industrial assembly-line workers exposed to repetitive tasks with short cycles were compared to 64 referent subjects with no repetitive exposure. Industrial workers performed tasks involving repetitive arm movements with static muscular work of the neck/shoulder muscles. In a multivariate model, there were statistically significant associations between exposure to repetitive work and diagnoses in the neck/shoulders. In addition, age, tendencies towards subjective muscular tension, and stress/worry were also associated with diagnoses in the neck/shoulders. Standardized evaluation of videotape recordings in 74 of the industrial workers revealed significant associations between neck flexion, and elevation and abduction of the arm with the prevalence of neck/shoulder diagnoses. The authors concluded that a substantial prevalence of neck and upper limb disorders are associated with repetitive work performed with a flexed neck and elevated and abducted arms. The authors also suggested that certain personal traits in some workers may potentiate the above association.

The epidemiologic evidence for increased risk of MSDs due to specific shoulder postures is strongest when there is exposure to a combination of risk factors such as force and repetitive work (Baron et al. 1991, Bjelle et al. 1979, English et al. 1995, Herberts et al. 1981, Ohlsson et al. 1994, Ohlsson et al. 1995). An example of this combination would be operating a powered hand tool while working overhead. Although most of the studies that investigate specific shoulder postures as an exposure variable are cross-sectional, prospective studies have revealed that the percent of work cycle spent with the shoulder elevated (Jonsson et al. 1988) or abducted (Kilbom et al. 1986, Kilbom and Persson 1987) predicted change to more severe neck and shoulder disorders.


There is increasing evidence that psychosocial and individual factors play a role in the development of work-related MSDs of the upper extremity (Bernard et al. 1994). The term “psychosocial” is commonly used in occupational health as an all-inclusive term to describe a variety of factors within and outside the workplace. Some of the psychosocial factors within the workplace that have been associated with work-related MSDs include: job dissatisfaction (Hopkins 1990; Tola et al. 1988); intensified workload (Bernard et al. 1993, Karasek et al. 1987, Theorell et al. 1991), monotonous work (Ekberg et al. 1994, Kvarnstrom and Halden 1983, Linton 1990), limited job control (Hales et al. 1994, Theorell et al. 1991), role ambiguity (Ekberg et al. 1994, Karasek et al. 1987), and limited social support from supervisors and co-workers (Hales et al. 1994, Hopkins 1990). These work and job environmental factors are often thought of as demands, or risk factors, that may pose a threat to health (Hurrell and Murphy 1992). Demands arising from roles outside of work, such as responsibilities associated with caring for a parent, spouse, or children may also constitute psychosocial factors that play a role in the development of MSDs. Interactions among factors within and outside of the workplace create what is referred to as a “stress process,” the results of which are thought to impact upon both health status and job performance (ILO 1986, Sauter and Swanson 1996, WHO 1989).

A number of individual factors that can influence a person’s response to risk factors for MSDs in the workplace include: age (Biering-Sorensen 1983, English et al. 1995, Ohlsson et al. 1994); gender (Armstrong et al. 1987, Chiang et al. 1993, Hales et al. 1994, Johansson 1994); anthropometry (Nathan et al. 1992, Werner et al. 1994); cigarette smoking (Svensson and Andersson 1983); and parity (Roquelaure et al. 1997). There may well be other individual lifestyle factors such as diet and exercise habits (Nathan et al. 1992), as well as a whole host of medical conditions, which affect an individual’s predisposition to developing MSDs. Some, but not all, epidemiologic studies have used statistical methods to take into account the effects of these individual factors (e.g., gender, age, body mass index, and parity) when investigating the associations between job tasks and MSDs. These statistical methods control for the confounding or modifying effects when determining the strength of association between MSDs and occupational factors. Studies that fail to control for the influence of individual factors may either mask or amplify the effects of work-related factors.

A model for the Prevention of occupational MSDs

The increasing incidence of occupational MSDs and the associated economic costs and production losses has prompted private enterprises, trade associations, labor organizations, and governmental agencies to search for effective occupational health and safety programs for the prevention of MSDs in occupational settings. Although many ergonomic prevention and intervention programs aimed at reducing MSDs have been implemented in the workplace, they have been devised based primarily on intuition and experience (Goldenhar and Schulte 1996). Theoretically-based interventions, however, can provide a plausible logical model of how an intervention will lead to the intended outcome and provides a conceptual framework for refining and improving existing prevention programs (Lipsey 1996). A clear conceptual model, or theory, of how the intervention will prevent MSDs is necessary in defining appropriate outcome measures for intervention research in occupational health and safety (Zwerling 1997).

When developing an ergonomics model for the prevention of MSDs it is useful to employ public health principles. In the context of disease progression (from no disease to symptomatic invasive disease), public health investigators recognize a continuum of prevention at three levels, primary, secondary, and tertiary (Halperin 1996, Last 1988) (Figure 2). Tertiary prevention refers to measures to reduce long-term impairment and disability. The diagnosis and treatment of an MSD would constitute tertiary prevention. Secondary prevention is the early detection of asymptomatic disease and prompt intervention when the disease is preventable or more easily treatable, such as in screening for breast cancer. An example of secondary prevention in ergonomics would be the early identification of carpal tunnel syndrome through nerve conduction screenings (Bingham et al. 1996). Primary prevention involves the prevention of disease before its initiation. In pediatric medicine for example, immunization for childhood diseases is an example of primary prevention. In ergonomics, primary prevention involves the development of interventions (often engineering changes) to eliminate the risk factors (i.e. awkward posture, excessive force, and high repetition) associated with the disorder. The most effective and distributive prevention strategy for occupational MSDs is through primary prevention.

Figure 2. The three stages of prevention in the disease process.

One of the corner stones of primary prevention strategies within the public health domain are activities involving recognition and evaluation of a health problem followed by intervention programs (Halperin, 1996). This public health paradigm can be easily applied and incorporated into a model for the prevention of MSDs through an ergonomics process. The ergonomic prevention model engaged by the authors is based on “Participatory Action Research” theory developed by Hugentobler et al. 1992 and Israel et al. 1992. According to Israel et al. (1992), participatory action research requires investigators to work collaboratively with the study population (i.e. the workforce). This research process is characterized by participation, cooperation, co-learning, system development, employee empowerment, and balancing research objectives with the objectives of the company (Israel et al. 1992).

As a focus point within the conceptual framework of participatory action research theory, several investigators have utilized an ergonomics process to encourage change in occupational settings (Moore and Garg 1996, Rosecrance and Cook 1996). This process is not unlike the public health paradigm involving recognition, evaluation, and intervention. The ergonomics process, however, consists of five specific but overlapping steps: (1) problem identification, (2) problem analysis, (3) solution development, (4) solution implementation, and (5) solution evaluation (Figure 3). The identification of MSDs and their associated risk factors is the first step in the ergonomics process. Once MSDs are identified, specific work tasks and methods are analyzed for detecting risk factors and developing potential solutions. Based on the findings from the analysis, a prioritization for solution development and implementation is planned. The implemented solutions are then evaluated. In the majority of cases, the initial solutions are imperfect, and therefore the situation is reanalyzed and the cycle repeated until a satisfactory result is obtained.

Figure 3. The ergonomics process model used in the primary prevention of occupational MSDs. (Original source: Orthopaedic Physical Therapy Clinics of North America, 5/2:274, 1996. With the kind permission of the Publisher)

The guideing principles of the ergonomic process include structure, scientific approach, participation by management, supervisors, workers, unions, and decision by consensus (Moore and Garg, 1996). A basic tenet of the ergonomics process is employee participation. The focus of employee involvement is to assure workers a sense of personal control over their workplace by educating them about and encouraging them to participate fully in workplace health and safety. This focus is not unlike that of employee empowerment (Wallerstein and Weinger 1992) and has the potential to affect the overall climate of the intervention process (Goldenhar and Schulte 1994). The ergonomics process model is a problem solving process and bears a strong resemblance to continuous learning and improvement which are basic elements in Deming’s philosophy of total quality management (TQM) (Deming 1986, Walton 1986). Among Deming’s (1986) 14 points for TQM are that managers are to provide vision, priorities, and structure but get out of the way and let people “own” their jobs. Experienced workers that perform job tasks involving high force and awkward postures often have ideas on how to make their jobs easier and more efficient. Worker solutions, however, may not come to fruition if they are not encouraged to express their ideas and become involved in the decision making process. In too many situations outside “experts” are called in and impose their solutions on the workers without regard to the people performing the actual tasks. The “expert” model may be inappropriate for many companies attempting to incorporate participatory ergonomic programs. Ergonomic experts will be more successful in conducting ergonomic prevention programs if they include both labor and management in planning and selecting interventions.


There is a consensus among employers, labor organizations, insurers, and industry associations that occupational MSDs are a major problem leading to adverse health and economic consequences. Scientific literature from various parts of the world has reported significant associations between occupational risk factors involving high repetition rates, excessive forces, and awkward postures and MSDs. When workers are exposed to multiple risk factors (such as repetitive drilling overhead), there is an increased likelihood of developing an occupational MSD. Although there is strong evidence for an association between work factors and MSDs, the causation of these disorders is multi-factorial. A worker’s susceptibility to MSDs can be influenced by psychosocial and individual factors. Many of these factors (i.e., age, smoking, physical activity, strength, anthropometry) are often beyond the control of the employer. A worker’s ability to respond to external work factors may be modified by his/her own internal capacity, such as tissue resistance to deformation when exposed to high force demands. The level, duration, and frequency of the loads imposed on tissues, as well as adequacy of recovery time, are critical components in whether increased tolerance (a training or conditioning effect) occurs, or whether reduced capacity occurs which can lead to MSDs. The relationship of these factors and the resulting risk of injury to the worker is complex and not fully understood.

Because of the multi-factorial nature of MSDs, an effective approach to dealing with work-related MSDs is a program consisting of primary prevention. Primary prevention programs have included the implementation of a cyclical ergonomics process involving continuous improvement. Key components of the ergonomics process consists of employee participation, management commitment, the identification of ergonomic hazards, the development of solutions and the evaluation of those solutions.

Although workplace prevention programs have been developed to reduce injury and illness, few have undergone systematic evaluation to determine their impact on health and safety outcomes. Consequently, many ergonomic intervention programs have been based on faith and expert judgement without convincing scientific evidence that these approaches are effective. Further research is needed to evaluate the effectiveness of ergonomic intervention efforts in terms of productivity, cost effectiveness, and reductions in occupationally related MSDs. A systematic evaluation can provide crucial guidance and corrective feedback for current and future occupational health and safety efforts. Intervention effectiveness research may provide evidence for effective ergonomic strategies and assure efficient use of limited resources in workplace prevention and intervention programs. 


Allender, E. (1974). “Prevalence, incidence, and remission rates of some common rheumatic diseases or syndromes.” Scand. J. Rheumatol. 3:145–153.

Armstrong, T.J., Buckle, P., Fine, L.J., Hagberg, M., Jonsson, B., and Kilbom, A. (1993). “A conceptual model for work-related neck and upper-limb musculoskeletal disorders.” Scand. J. Work Environ. Health 19:73–84.

Armstrong, T.J., Fine, L.J., Goldstein, S.A., Lifshitz, Y.R., and Silverstein, B.A. (1987). “Ergonomic considerations in hand and wrist tendinitis.” J. Hand Surg. 12A:830–837.

Amano, M., Gensyo, U., Nakajima, H., and Yatsuki, K. (1988). “Characteristics of work actions of shoe manufacturing assembly line workers and a cross-sectional factor control study on occupational cervicobrachial disorders.” Jpn. J. Ind. Health 30:3–12.

Baron, S., Milliron, M., Habes, D., and Fidler, A. (1991). Hazard evaluation and technical assistance report: Shoprite Supermarkets, New Jersey–New York. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, NIOSH Report No. HHE 88–344–2092.

Bernard, B., Sauter, S., and Fine, L.J. (1993). Hazard evaluation and technical assistance report: Los Angeles Times, Los Angeles, CA. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, NIOSH Report No. HHE 90–013–2277.

Bernard, B., Sauter, S., Fine, L.J., Petersen, M., and Hales, T. (1994). “Job task and psychosocial risk factors for work-related musculoskeletal disorders among newspaper employees.” Scand. J. Work Environ. Health 20:417– 426.

Biering-Sorensen, F. (1983). “A prospective study of low-back pain in a general population: Occurrence, recurrence, and aetilogy.” Scand. J. Rehabil. Med. 15:81–88.

Bingham, R.C., Rosecrance, J.C., and Cook, T.M. (1996). “Prevalence of abnormal median nerve conduction in applicants for industrial jobs.” Am. J. Ind. Med. 30:355–361.

BLS (1997). Workplace Injuries and Illnesses in 1996. Washington, DC: U.S. Department of Labor, Bureau of Labor Statistics.

Bjelle, A., Hagberg, M., and Michaelsson, G. (1979). “Clinical and ergonomic factors in prolonged shoulder pain among industrial workers.” Scand. J. Work Environ. Health 5:205–210.

Bovenzi, M. (1994). “Hand-arm vibration syndrome and dose-response relation for vibration-induced white finger among quarry drillers and stone carvers.” Occup. Environ. Med. 51:603–611.

Bystrom, S., Hall, C., Welander, T., and Kilbom, A. (1995). “Clinical disorders and pressure-pain threshold of the forearm and hand among automobile assembly line workers.” J. Hand Surg. 20B:782–790.

C.W.C.I. (1993). Report on CTDs. San Francisco, CA: California Workers’ Compensation Institute.

Chatterjee, D. (1992). “Workplace upper limb disorders: a prospective study with intervention.” J. Occup. Med. 42:129–136.

Chiang, H., Ko, Y., Chen, S., Yu, H., Wu, T., and Chang, P. (1993). “Prevalence of shoulder and upper-limb disorders among workers in the fish-processing industry.” Scand. J. Work Environ. Health 19:126–131.

Deming, W.E. (1986). Out of the Crises. Cambridge: Massachusetts Institute of Technology, Center for Advanced Engineering Study.

Ekberg, K., Bjorkqvist, B., Malm, P., Bjerre-Kiely, B., Karlsson, M., and Axelson. O. (1994). “Case-control study of risk factors for disease in the neck and shoulder area.” Occup. Environ. Med. 51:262–266.

English, C.J., Maclaren, W.M., Court-Brown, C., Hughes, S.P.F., Porter, R.W., and Wallace, W.A. (1995). “Relations between upper limb soft tissue disorders and repetitive movements at work.” Am. J. Ind. Med. 27:75–90.

Gerr, F., Letz, R., and Landrigan, P.J. (1991). “Upper-extremity musculoskeletal disorders of occupational origin.” Ann. Rev. Public Health 12:543–566.

Goldenhar, L.M., and Schulte, P.A. (1994). “Intervention research in occupational health and safety.” J. Occup. Med. 36:763–775.

Goldenhar, L.M., and Schulte, P.A. (1996). “Methodological issues for intervention research in occupational health and safety.” Am. J. Ind. Med. 29:289–294.

Hagberg, M., Morgenstern, H., and Kelsh, M. (1992). “Impact of occupations and job tasks on the prevalence of carpal tunnel syndrome.” Scand. J. Work Environ. Health 18:337– 345.

Hagberg, M., and Wegman, D.H. (1987). “Prevalence rates and odds ratios of shoulder-neck diseases in different occupational groups.” Br. J. Ind. Med. 44:602–610.

Hales, T.R., Sauter, S.L., Peterson, M.R., Fine, L.J., Putz-Anderson, V., Schleifer, L.R., Ochs T.T., and Bernard B.P. (1994). “Musculoskeletal disorders among visual display terminal users in a telecommunications company.” Ergonomics 37:1603–1621.

Halperin, W.E. (1996). “The role of surveillance in the hierarchy of prevention.” Am. J. Ind. Med. 29:321–323.

Herberts, P., Kadefors, R., Andersson, G., and Petersen, I. (1981). “Shoulder pain in industry: an epidemiological study on welders.” Acta. Orthop. Scand. 52:299–306.

Hopkins, A. (1990). “Stress, the quality of work, and repetition strain injury in Australia.” Work and Stress 4:129–138.

Hugentobler, M.K., Israel, B.A., and Schurman, S.J. (1992). “An action research approach to workplace health: Integrating methods.” Health Educ. Q. 19:55–76.

Hurrell, J.J. and Murphy, L.R. (1992). “Psychological job stress.” In: Rom WN, ed. Environmental and Occupational Medicine. 2nd ed. New York, NY: Little, Brown and Company, pp. 675–684.

ILO (1986). Psychosocial factors at work: recognition and control. Geneva, Switzerland: International Labour Office.

Israel, B.A., Schurman, S.J., and Hugentobler, M.K. (1992). “Conducting action research: Relationships between organization members and researchers. J. Appl. Behav. Sci. 28:75–101.

Johansson, J.A. (1994). “Work-related and non-work-related musculoskeletal symptoms.” Appl. Ergonomics 25:248–251.

Jonsson, B.G., Persson, J., and Kilbom, A. (1988). “Disorders of the cervicobrachial region among female workers in the electronics industry: a two-year follow-up.” Int. J. Ind. Ergonomics 3:1–12.

Karasek, R.A., Gardell, B., and Lindell, J. (1987). “Work and non-work correlates of illness and behaviour in male and female Swedish white collar workers.” J. Occup. Behav. 8:187–207.

KÁKOSY, T. (1994). “Tunnel syndromes of the upper extremities in workers using hand-operated vibrating tools.” Med. Lav. 85:474–480.

Kilbom, A., Horst, D., Kemfert, K., and Richter, A. (1986). “Observation methods for reduction of load and strain on the human body – a review.” Abetarskyddsstyrelsen Publikation Service 171:92.

Kilbom, A. and Persson, J. (1987). “Work technique and its consequences for musculoskeletal disorders.” Ergonomics 30:273–279.

Kuorinka, I. and Forcier, L. (1995). Work-related Musculoskeletal Disorders (WMSDs): A Reference Book for Prevention. London, England: Taylor & Francis.

Kuorinka, I. and Koskinen, P. (1979). “Occupational rheumatic diseases and upper limb strain in manual jobs in a light mechanical industry.” Scand. J. Work Environ. Health 5 (Suppl 3):39–47.

Kurppa, K., Viikari-Juntura, E., Kuosma, E., Huuskonen, M., and Kivi, P. (1991). “Incidence of tenosynovitis or peritendinitis and epicondylitis in a meat-processing factory.” Scand. J. Work Environ. Health 17:32–37.

Kvarnstrom, S. and Halden, M. (1983). “Occupational cervicobrachial disorders in an engineering company.” Scand. J. Rehabil. Med. 8:1–114.

Last, J.M. (1988). A Dictionary of Epidemiology. 2nd edition. New York: Oxford University Press.

Leclerc, A., Franchi, P., Cristofari, M.F., Delemotte, B., Mereau, P., Teyssier-Cotte, C., and Touranchet, A. (1998). “Carpal tunnel syndrome and work organisation in repetitive work: a cross sectional study in France.” Occup. Environ. Med. 55:180–187.

Linton, S.J. (1990). “Risk factors for neck and back pain in a working population in Sweden.” Work and Stress 4:41–49.

Lipsey, M.W. (1996). “Key issues in intervention research: A program evaluation perspective.” Am. J. Ind. Med. 29:298–302.

Luopajarvi, T., Kuorinka, I., Virolainen, M., and Holmberg, M. (1979). “Prevalence of teno-synovitis and other injuries of the upper extremities in repetitive work.” Scand. J. Work Environ. Health 5(Suppl 3):48–55.

Lusa-Moser, S., Viikari-Juntura, E., Punakallio, R., and Luukkonen, R. (1997). “Factors associated with musculoskeletal symptoms of finnish fire fighters.” In: From Experience to Innovation. (P. Seppala, T. Luopajarvi, C.H. Nygard and M. Mattila Eds.) Proceedings of the 13th Congress of the International Ergonomics Association, Tampere, Finland. Finnish Institute of Occupational Health, Helsinki. vol 4, pp:75–77.

Maeda, K., Hirayama, H., and Takamatsu, M. (1977). “Occupational cervicobrachial disorders in workwomen in assembly lines of a cigarette factory.” Japan J. Ind. Health 19:8–21.

Maeda, K., Horiguchi, S., and Hosokawa, M. (1982). “History of the studies on occupational cervicobrachial disorders in Japan and remaining problems.” J. Human Ergol. 11:17–29.

McCormack, R.R., Inman, R.D., Wells, A., Berntsen, C., and Imbus, H.R. (1990). “Prevalence of tendinitis and related disorders of the upper extremity in a manufacturing workforce.” J. Rheumatol. 17:958–964.

Moore, J.S. (1992). “Carpal tunnel syndrome.” Occup. Med. State Art Rev. 7:741– 763.

Moore, J.S. and Garg, A. (1994). “Upper extremity disorders in a pork processing plant: relationships between job risk factors and morbidity.” Am. Ind. Hygiene Assoc. J. 55:703–715.

Moore, J.S. and Garg, A. (1996). “Use of participatory ergonomic teams to address musculoskeletal hazards in the red meat packing industry.” Am. J. Ind. Med. 29:402–408.

Muruka, A.O. (1997). “The role of height in musculoskeletal health: A case study of tea pickers of Kericho and Kisii in Kenya.” In: From Experience to Innovation. (P. Seppala, T. Luopajarvi, C.H. Nygard and M. Mattila Eds.) Proceedings of the 13th Congress of the International Ergonomics Association, Tampere, Finland. Finnish Institute of Occupational Health, Helsinki. vol 4, pp:377–380.

Nathan, P.A., Keniston, R.C., Myers, L.D., and Meadows, K.D. (1992). “Obesity as a risk factor for slowing of sensory conduction of the median nerve in industry: A cross-sectional and longitudinal study involving 429 workers.” J. Occup. Med. 34:379–383.

NIOSH (1996). National occupational research agenda. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 96–115.

NIOSH (1997). Musculoskeletal disorders and workplace factors: A critical review of epidemiologic evidence for work-related musculoskeletal disorders of the neck, upper extremity, and low back. Cincinnati, OH: U.S. Department of Health and Human Services, Public Health Service, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 97–141.

Ohlsson, K., Hansson, G.A., Balogh, I., Stromberg, U., Palsson, B., Nordander, C., Rylander, L., and Skerfving, S. (1994). “Disorders of the neck and upper limbs in women in the fish processing industry.” Occup. Environ. Med. 51:826–832.

Ohlsson, K., Attewell, R., Paisson, B., Karlsson, B., Balogh, I., Johnsson, B., Ahlm, A., and Skerfving, S. (1995). “Repetitive industrial work and neck and upper limb disorders in females.” Am. J. Ind. Med. 27:731–747.

PÓrszÁsz, J., TasnÁdi J., Bereczki I., and Varga J. (1997). “The pattern of gripping force during bus driving.” Cent. Europ. J. Occup. Environ. Med. 3:67–80.

Punnett, L., Robins, J.M., Wegman, D.H., and Keyserling, W.M. (1985). “Soft-tissue disorders in the upper limbs of female assembly workers: impact of length of employment, work pace, and selection.” Scand. J. Work Environ. Health 11:417–425.

Putz-Anderson, V. (1988). Cumulative Trauma Disorders: A Manual for Musculoskeletal Diseases of the Upper Limbs. Cincinnati, National Institute for Occupational Safety and Health.

Riihimaki, H. (1995). “Hands up or back to work – future challenges in epidemiologic research on musculoskeletal diseases.” Scand. J. Work Environ. Health 21:401–403.

Roquelaure, Y., Mechali, S., Dano, C., Fanello, S., Benetti, F., Bureau, D., Mariel J., Martin Y-H., Derriennic F., and Penneau-Fontbonne, D. (1997). “Occupational and personal risk factors for carpal tunnel syndrome in industrial workers.” Scand. J. Work Eviron. Health. 23:364–369.

Rosecrance, J.C. and Cook, T.M. (1996). “Ergonomic Intervention in Newspaper Production.” In: Orthopaedic Physical Therapy Clinics of North America: Ergonomics, Part 1 (K. M. Piegorsch, ed.) W.B. Saunders Company, Philadelphia, pp. 273–286.

Roto, P. and Kivi, P. (1984). “Prevalence of epicondylitis and tenosynovitis among meat cutters.” Scand. J. Work Environ. Health 10:203– 205.

Sauter, S.L. and Swanson, N.G. (1996). “Psychological aspects of musculoskeletal disorders in office work.” In: Moon S, Sauter S, eds. Psychosocial factors and musculoskeletal disorders. London, England: Taylor and Francis.

Silverstein, B.A., Fine, L.J., and Armstrong, T.J. (1987). “Occupational factors and the carpal tunnel syndrome.” Am. J. Ind. Med. 11:343– 358.

Sommerich, C.M., McGlothin, J.D., and Marras, W.S. (1993). “Occupational risk factors associated with soft tissue disorders of the shoulder: a review of recent investigations in the literature.” Ergonomics 36:697–717.

Stock, S.R. (1991). “Workplace ergonomic factors and the development of musculoskeletal disorders of the neck and upper limbs: a meta-analysis.” Am. J. Ind. Med. 19:87–107.

Svensson, H. and Andersson, G.B.J. (1983). “Low- back pain in 40- to 47-year old men: work history and work environment factors.” Spine 8:272–276.

Theorell, T., Harms-Ringdahl, K., Ahlberg-Hulten, G., and Westin, B. (1991). “Psychosocial job factors and symptoms from the locomotor system: a multicausal analysis.” Scand. J. Rehabil. Med. 23:165–173.

Tola, S., Riihimaki, H., Videman, T., Viikari-Juntura, E., and Hanninen, K. (1988). “Neck and shoulder symptoms among men in machine operating, dynamic physical work and sedentary work.” Scand. J. Work Environ. Health 14:299–305.

Viikari-Juntura, E. (1995). “The role of physical stressors in the development of hand/

wrist, and elbow disorders.” In: Gordon SL, Blair SJ, Armstrong, et al., eds. Pathophysiology and Clinical Factors in Upper Extremity Repetitive Motion Syndromes. Bethesda, MD: American Academy of Orthopedic Surgeons.

Wallerstein, N. and Weinger, M. (1992). “Health and safety education for worker empowerment.” Am. J. Ind. Med. 22:619–635.

Werner, S., Albers, J.W., Franzblau, A., and Armstrong, T.J. (1994). “The relationship between body mass index and the diagnosis of carpal tunnel syndrome.” Muscle & Nerve. 17:632–636.

Winkel, J. and Westgaard, R. (1992). “Occupational and individual risk factors for shoulder-neck complaints. Part II: The scientific basis (literature review) for the guide.” Int. J. Ind. Ergonomics 10:85–104.

Wright. W.C. (1940). Diseases of Workers. (The Latin text De Morbis Artificum Diatriba of Ramazzini, 1713, translated by Wright) Chicago, Ill: University of Chicago Press.

Young, V. L., Nemecek, J. R., Higgs, P. E., and Ball D., J. (1992). “Cumulative trauma disorders: An overview of the problem.” J. Occup. Rehabil. 3:139–156.

Yu, I.T.S. and Wong, T.W. (1996). “Musculoskeletal problems among VDU workers in a Hong Kong bank.” Occup. Med. 46:275–280.

Walton, M. (1986). The Deming Management Method. New York, Perigee Books.

Webster, B.S. and Snook, S.H. (1994). “The cost of compensable upper extremity cumulative trauma disorders.” J. Occup. Med. 36:713–727.

WHO (1985). Identification and Control of Work-Related Diseases. Geneva, Switzerland: World Health Organization. WHO Technical Report Series 714.

WHO (1989). “Work with visual display terminals: psychosocial aspects and health.” J. Occup. Med. 31:957–968.

Zwerling, C., Daltroy, L.H., Fine, L.J., Johnston, J.J., Melius, J., and Silverstein, B.A. (1997). “Design and conduct of occupational injury intervention studies: A review of evaluation strategies.” Am. J. Ind. Med. 32:164–179. 

| Back |

Posted: 17 November 1998