Hip pain onset in relation to cumulative workplace and leisure time mechanical load: a population-based case-control study

Objective: In an unselected community sample of adults, to assess the role and importance of exposure to mechanical factors both at work and leisure in the aetiology of hip pain.

Method: A population based prevalence case-control study. Cases and controls were identified from a population survey of 3847 subjects registered with two general practices in Cheshire, United Kingdom. All subjects received a postal questionnaire which inquired about hip pain during the past month. An occupational history was obtained, including exposure to each of seven physical demands. Information was also obtained on history of participation in eight common sporting activities.

Results: 88% of those invited to participate returned a completed questionnaire. The 352 subjects with hip pain were designated as cases, and the remaining 3002 subjects as controls. In people ever employed, hip pain was significantly associated with high cumulative workplace exposure (before onset) of walking long distances over rough ground, lifting/moving heavy weights, sitting for prolonged periods, walking long distances, frequent jumping between different levels, and standing for prolonged periods. Odds ratios (ORs) in the higher exposure categories ranged from 1.46 to 2.65. Cumulative exposure to three sporting activities was significantly associated with hip pain: track and field sports, jogging, and walking, with odds ratios varying between 1.57 to 1.94. On multivariate analysis three factors were independent predictors of hip pain onset: cumulative exposure of sitting for prolonged periods (higher exposure v not exposed: OR=1.82, 95% confidence interval (CI) 1.13 to 2.92), lifting weights >50 lb (23 kg) (OR=1.74, 95% CI 1.06 to 2.86) (both relating to the workplace), and walking as a leisure activity (OR=1.97, 95% CI 1.32 to 2.94). The population attributable risk associated with each of these activities was 21%, 13%, and 16%, respectively.

Conclusions: Cumulative exposure to some workplace and sporting "mechanical" risk factors for hip osteoarthritis (OA) appear to be related to hip pain in general-some (but not all) have previously been related to hip OA. Because these are common workplace or leisure time activities their attributable risk is high.