AMERICAN JOURNAL OF INDUSTRIAL MEDICINE 52:479–490 (2009) Quantitative Exposure-Response Relations Between Physical Workload and Prevalence of Lateral Epicondylitis in a Working Population Z. Joyce Fan, PhD, 1 Barbara A. Silverstein, PhD, MPH, CPE, 1 Stephen Bao, PhD, 1 Dave K. Bonauto, MD, MPH, 1 Ninica L. Howard, MSE, 1 Peregrin O. Spielholz, PhD, 1 Caroline K. Smith, MPH, 1 Nayak L. Polissar, PhD, 2 and Eira Viikari-Juntura, MD, PhD 3 Background Lateral epicondylitis is a common work-related musculoskeletal disorder. The objective of this study was to identify risk factors associated with lateral epicondylitis among active workers. Methods Seven-hundred thirty-three workers in 12 Washington worksites participated in structured interviews, physical examinations, and individual exposure assessments of biomechanical and psychosocial factors. Multivariable logistic modeling was used. Results Thirty-eight subjects (5.2%) had lateral epicondylitis. Age (36–50 years-old), being female, and low social support at work were significant risk factors. Frequency of forceful exertion (5 vs. <1 times/min (OR 5.17, 95%CI 1.78–15.02), and 1 to <5 vs. <1 (OR 4.47, 95%CI 1.57–13.71)) and forearm supination at 458 for 5% of the time with high lifting force (OR ¼ 2.98, 95% CI 1.18–7.55) were significant physical load factors. Conclusions Frequency of forceful exertion or a combination of forearm supination and forceful lifting were significant physical factors and should be considered for prevention strategies. Am. J. Ind. Med. 52:479 – 490, 2009. ß 2009 Wiley-Liss, Inc. KEY WORDS: lateral epicondylitis; prevalence; quantitative physical workload; active workers INTRODUCTION Lateral epicondylitis (also known as tennis elbow) is one of the major upper extremity musculoskeletal disorders (UEMSD) in active workers [Ware et al., 1996; Silverstein and Adam, 2006]. Previous reports from different countries indicate that the prevalence of lateral epicondylitis ranges from 2% to 14.5% in working populations [McCormack et al., 1990; Viikari-Juntura et al., 1991; Chiang et al., 1993; Ware et al., 1996; Ono et al., 1998] and tend to be more on the dominant elbow [Shiri et al., 2007]. In Washington State, non-traumatic epicondylitis had an annual compensable workers’ compensation claims incidence rate of 4.7 per 10,000 full time employees, resulting in an average of 263 lost work days per claim and an average annual direct cost of more than $12 million [Silverstein and Adam, 2006]. The relationship between physical load at work and the occurrence of lateral epicondylitis has been the subject of several studies. Longer durations of employment in stren- uous jobs [McCormack et al., 1990; Ritz, 1995; Ono et al., 1998], forceful work tasks [Kurppa et al., 1991; Leclerc et al., 2001], the combination of forceful and repetitive activities of the upper extremity [Werner et al., 2005; Shiri et al., 2006], and the combination of either forceful or repetitive activities with extreme non-neutral posture of hands and arms [Ono et al., 1998] have been found to be related to lateral ß 2009 Wiley-Liss, Inc. 1 Safety & Health Assessment and Researchfor Prevention (SHARP),Washington State Department of Labor & Industries,OlympiaWashington 2 TheMountain-Whisper-LightStatistical Consulting,Seattle,Washington 3 Finnish Institute of Occupational Health,Helsinki,Finland *Correspondenceto:FanZ.Joyce,243IsraelRdSEBldg3,Tumwater,WA98501. E-mail: fanj235@LNI.wa.gov Accepted10February2009 DOI10.1002/ajim.20700.PublishedonlineinWileyInterScience (www.interscience.wiley.com)