Association between Cumulative Joint Loading from Occupational Activities and Knee Osteoarthritis

Objective: To determine the associations between cumulative occupational physical load (COPL) and three definitions of knee osteoarthritis. Methods: Cross-sectional analyses were performed from two population-based cohorts (n=327). Eligible symptomatic participants were those with pain, aching, or discomfort in or around the knee on most days of a month at any time in the past and any pain in the past 12 months. Asymptomatic participants responded “no” to both knee pain questions. Self-reported COPL was calculated over each participant’s lifetime, and then categorized into quarters (i.e., QCOPL). Radiographic osteoarthritis (ROA) and symptomatic osteoarthritis (SOA) were defined by Kellgren Lawrence grade >2, with SOA also including pain. Magnetic resonance imaging osteoarthritis (MRIOA) was defined using criteria by Hunter and associates. Logistic regression, adjusted with population weights, examined the associations between QCOPL and ROA, SOA, and MRI-OA, respectively, after controlling for covariates and two-way interactions. Results: Participants were on average 58.5 (SD=11.0) years old with a BMI of 26.3 (SD=4.7). Of those, 109(33.3%) had ROA, 102(31.2%) had SOA and 131(40.1%) had MRI-OA. Compared with QCOPL-1, increased odds of ROA were found for QCOPL-4 (Odds ratio (OR)=3.15; 95% Confidence Interval (CI)=1.02, 9.70) and QCOPL-3 (OR=4.19; 95% CI=1.55, 11.34). Statistically significant relationships were found in SOA (QCOPL-4: OR=8.16; 95% CI=1.89, 35.27; QCOPL3: OR=5.73; 95% CI=1.36, 24.12) and MRI-OA (QCOPL-4: OR=9.54; 95% CI=2.65, 34.27; QCOPL-3: OR=9.04; 95% CI=2.65, 30.88; QCOPL-2: OR=7.18; 95% CI=2.17, 23.70.) Conclusion: Occupational activity is associated with knee OA with dose-response relationships observed in SOA and MRI-OA.Medicine, Faculty ofMedicine, Department ofPhysical Therapy, Department ofPopulation and Public Health (SPPH), School ofRheumatology, Division ofReviewedFacultyGraduat