Knee-straining work activities, self-reported knee disorders and radiographically determined knee osteoarthritis.

OBJECTIVES: Earlier studies indicate an increased risk of knee disorders in trades with knee-straining work positions, but no dose-response correlation has yet been documented. This study examined whether self-reported knee complaints and radiologically diagnosed knee osteoarthritis are dose-related to kneeling and squatting work positions.
METHODS: Worktasks for floor layers and carpenters were video-recorded, and the time spent in knee-straining work positions was quantified. A questionnaire study included 133 floor layers, 506 carpenters, and 327 compositors, all without earlier acute knee trauma. Radiological examinations were carried out on a stratified sample (N = 150) from the questionnaire study. The individual exposure was calculated from the amount of knee strain quantified in the video-recorded worktasks, the self-reported time spent in the worktask, and the number of years in the trade. Statistical analyses were carried out with a binary logistic regression model, adjusting for age, body mass index, smoking, and knee-straining sports activities.
RESULTS: The odds ratios for self-reported knee complaints and radiographically determined knee osteoarthritis were increased in relation to the degree of knee-straining work demands for workers with low-to-moderate, high, and very high exposure to knee-straining work demands in a comparison with the reference group, without knee-stressing work activities.
CONCLUSIONS: The results indicate that there is a dose-response correlation between knee-straining work activities and the development of self-reported knee complaints and radiologically diagnosed knee osteoarthritis.