Objectives To investigate the risk of total hip replacement (THR) due to primary osteoarthritis (OA) in relation to cumulative occupational mechanical exposures and lifestyle factors.

Method In a population of Danish employees, we identified first-time THR cases in the National Patient Register. For each case, two age- and sex-matched controls were drawn. In total 2500 randomly selected case-control sets were mailed a questionnaire entailing job history, weight (present and at age 25), height, smoking and sports activities at age 25. We used a job exposure matrix to calculate cumulative exposures in the work environment. Exposure estimates were expressed according to the pack-year concept of smoking (cumulative lifting = ton-years). We used conditional logistic regression.

Results 71% of case-control sets contributed to the study. The adjusted odds ratio for exposure to at least 20 ton-years was 1.35 (95% CI 1.05–1.74) for men. When analysing frequent lifting as risk factor, the adjusted OR reached 1.26 (95% CI 0.99–1.61). There were no such increases for women. We controlled for body mass index, sports participation at age 25 and previous trauma towards the knees.

Conclusions When using a job exposure matrix we found a modest increased risk of THR in relation to cumulative lifting for men. For women no increased risk was seen.