From The Ergoweb® Learning Center

Strong Causal Risk Factor/WMSD Evidence Remains Elusive

Since publication of the exhaustive 1997 NIOSH study, “Musculoskeletal Disorders and Workplace Factors,” there has not been a detailed follow-up analysis of recent research findings involving the relationship between risk factors and work-related musculoskeletal disorders (WMSDs).  A recent Canadian study reviewed the literature published since 1997 and did not find strong causal evidence between WMSDs and any specific risk factor among 63 selected papers.

However, it was determined that there is reasonable causal evidence for the following relationships:

  • Neck disorders with psychosocial factors, smoking, gender, posture and co-morbidity
  • Low back disorders with awkward posture, heavy physical work, lifting, psychosocial factors, younger age and high BMI
  • Non-specified upper limb disorders with co-morbidities
  • Shoulder disorders with heavy physical work and psychosocial factors
  • Elbow/forearm disorders with awkward posture, co-morbidity, repetitive work and older age
  • Wrist/hand disorders with prolonged computer work, heavy physical work, high BMI, older age, female gender, awkward posture and repetitive work
  • Non-specified lower limb disorders with no specific risk factor
  • Hip disorders with lifting and heavy physical work
  • Knee disorders with awkward posture, lifting,repetition and co-morbidity
  • Fibromyalgia and non-specified WMSDs with no specific risk factor

The Bottom Line – How This Applies To Ergonomists

This analysis confirms many of the prior identified physical, psychosocial and personal risk factors that have been associated with WMSDs. The study also reveals the paucity of strong causal evidence for commonly perceived risk factors and WMSDs.  Lack of epidemiologic support does not prove that a perceived risk factor is benign.  Rather, this review underscores the need for high quality studies involving risk factors.

Other Key Study Points

Citing other papers, the authors clarified the magnitude of WMSDs by noting:

  • 600,000 United States workers experience lost-work days as a result of WMSDs on a yearly basis
  • WMSDs are the most expensive form of work disability (In Germany, 38 billion Euros in 2002 and 26 billion Canadian dollars in 1998)

Study Design

Search terms of musculoskeletal disorders, work and risk factors were applied to four electronic data bases (Cinahl, Embase, Medline and the Cochrane Library) for the years 1997 to 2008. From 1,761 unique articles, a screening method reduced the number of acceptable articles to 63 (among other factors, only case-control or cohort studies were included).  A prospective cohort design characterized 51 of the reviewed papers.

Risk factors associated with work-related musculoskeletal disorders were categorized into affected body part, type of risk factor (biomechanical, psychosocial or individual), and level of evidence.

Assessment of a causal relationship was based on classic epidemiologic principles: strength of association, consistency between studies, temporality, dose-response relationship and coherence.  From the supporting information, a risk factor was classified as having strong evidence, reasonable evidence, or insufficient evidence relative to causation of a WMSD.


This position paper can be acquired at:

Article Title: Risk Factors for Work-Related Musculoskeletal Disorders: A Systematic Review of Recent Longitudinal Studies

Publication:  American Journal of Industrial Medicine, 2009

Authors: B R da Costa and E R Vieira

This article originally appeared in The Ergonomics Report™ on 2009-10-07.