Sitting may increase risk for radiographic incidence and progression of knee osteoarthritis over 2 years: Data from a large cohort study.

Objectives: To examine the association of leisure-time sitting with radiographic incidence and progression of knee osteoarthritis (OA) over 2 years, and to determine whether worktime sitting modifies this association.

Methods: We included adults with or at high risk for knee OA who enroled in the Osteoarthritis Initiative (OAI). Participants reported leisure-time sitting (≤4 vs. >4 h/day) and worktime sitting (frequent vs. infrequent) at enrolment, and had bilateral knee radiographs at enrolment and 2 years later. Our outcome, radiographic knee OA incidence/progression (yes/no), was defined as any increase in Kellgren-Lawrence grade over 2 years. We examined the association of leisure-time sitting (≤4 vs. >4 h/day) with risk of radiographic knee OA incidence/progression using binary linear regression, adjusting for potential confounders. We stratified by worktime sitting (frequent vs. infrequent) and repeated our analysis.

Results: We included 4254 adults (mean age 61 years; 58% women; mean body mass index 29 kg/m ) who contributed a total of 8127 knees. Adults with >4 h/day of leisure-time sitting had 25% higher risk (adjusted risk ratio [RR] 1.25, 95% confidence interval [95% CI] 1.08-1.50) for radiographic knee OA incidence/progression compared with adults with ≤4 h/day of leisure-time sitting (referent group). Importantly, this association was intensified (RR 1.60, 95% CI 1.19-2.33) among adults with frequent worktime sitting, but was attenuated (RR 1.11, 95% CI 0.89-1.39) among adults with infrequent worktime sitting.

Conclusions: Higher leisure-time sitting (>4 h/day) may be associated with greater risk for radiographic knee OA incidence/progression over 2 years. Furthermore, this association was intensified among adults who also reported frequent worktime sitting.