• Epidemiology
• Musculoskeletal
• Psychosocial
• Physical work

Musculoskeletal pain, especially in the back and upper limb, is a major cause of disability in people of working age. Observational studies have consistently demonstrated associations with occupational activities such as heavy lifting and forceful repetitive movements of the wrist and hand, which physically stress relevant anatomical structures.1 Thus, although there is often no demonstrable underlying injury to tissues that would account for reported symptoms,2 preventive efforts in the workplace have focused mainly on ergonomic measures designed to reduce mechanical loading. Disappointingly, randomised controlled trials of ergonomic interventions have failed to demonstrate major benefits in the prevention either of low back3 or upper limb pain,4 although evidence on the latter is rather sparse. Moreover, research has revealed large international variation in the prevalence of disability from musculoskeletal pain, even among workers with similar jobs,5 and also major temporal changes within countries that cannot be explained by biomechanical factors.6 These observations indicate that there must also be other important causes.

Another notable epidemiological feature of musculoskeletal pain is its tendency to recur, and to affect multiple anatomical …