Workplace policies and prevalence of knee osteoarthritis: the Johnston County Osteoarthritis Project.

ABSTRACT

OBJECTIVE: Previous studies on work and knee osteoarthritis (KOA) have been primarily focused on physical demands; very little is known about work-related organisational policies and KOA risks and outcomes. We examined the associations between workplace policies and KOA in a community-based population in the USA. METHODS: The associations between employment offering accommodations (switch to physically less demanding jobs; part-time work for people needing reduced time) and benefits policies (paid sick leave; disability payment) with KOA outcomes (knee symptoms; symptomatic KOA [sKOA]; asymptomatic radiographic KOA [rKOA]) were analysed in participants (n = 1639) aged <65 years old and with completed employment histories and knee radiographs at baseline examination of the Johnston County Osteoarthritis Project. Multiple logistic regression models were used to estimate the prevalence odds ratios (ORs) of KOA associated with each workplace policy, adjusting for sociodemographic features, lifestyle factors, knee injuries, body mass index and other workplace characteristics. We used propensity score models to evaluate the differential selection in employment offering favourable policies and adjust for this potential bias accordingly. RESULTS: Individuals employed in workplaces offering better policies had significantly less knee symptoms. Lower sKOA prevalence was noted in workplaces offering job-switch accommodation (8% vs. 13%), paid sick leave (9% vs. 16%) and disability payment (8% vs. 16%) than their counterparts. In multivariable models, the difference in sKOA prevalence was statistically significant for paid sick leave (adjusted OR 0.58, 95% CI 0.37 to 0.91) and disability payment policies (adjusted OR 0.54, 95% CI 0.35 to 0.85). Even among those without overt knee-related symptoms, a similar pattern of negative association between workplace policies and rKOA was present and remained robust after propensity score adjustment. CONCLUSION: The negative associations between KOA and workplace policies raise concerns about possible employment discrimination or beneficial effects of workplace policies. Longitudinal studies are needed to clarify the dynamic complexities of KOA risks and outcomes in relation to workplace policies.