Abstract
OBJECTIVE: Occupations involving greater physical activity may increase risk for knee osteoarthritis (OA). Existing studies have not evaluated work-related physical activity before OA onset. Hence, we aimed to evaluate the association between work-related physical activity and knee OA incidence. METHODS: We performed a person-based longitudinal study using Osteoarthritis Initiative (OAI) data among people who volunteered or worked for pay without baseline radiographic knee OA or knee pain. Bilateral knee radiographs were obtained at baseline and annual follow-ups. We defined radiographic OA as Kellgren-Lawrence grade ≥2. Questions from the Physical Activity Scale for the Elderly at baseline and annual OAI visits provided information about work-related physical activity level and hours. We performed logistic regression with work-related physical activity level ( mainly sitting , standing and some walking , walking while handling some materials ) and hours as predictors. The outcome was incident person-based radiographic OA within the ensuing 12 months, over 48 months. RESULTS: Among 951 participants (2819 observations), higher work-related physical activity levels had greater adjusted ORs for incident radiographic OA (people with jobs with standing and some walking : 1.11 (0.60-2.08), and walking while handling some materials : 1.90 (1.03-3.52), when compared with those with mainly sitting work-related activity ). There was no association between number of hours worked and incident radiographic OA. CONCLUSIONS: People performing work that require walking while handling some materials have greater odds of incident knee OA than those with jobs mostly involving sitting. Strategies are needed to mitigate risk factors predisposing them to radiographic OA.