Session Title: Osteoarthritis - Clinical Aspects
Session Type: Abstract Submissions (ACR)
Background/Purpose: Knee osteoarthritis (OA) results from the interaction of multiple risk factors, one of which may be physically demanding occupations. The purpose of this study was to determine the association between cumulative occupational physical load (COPL) and the presence of knee OA, defined as Symptomatic Radiographic Osteoarthritis (SOA) or Magnetic Resonance Imaging Osteoarthritis (MRI-OA).
Methods: This was a cross-sectional analysis of symptomatic (n=255) and asymptomatic (n=72) knee cohorts recruited as a random sample from the same population. Participants were 40 to 79 years old. Inclusion criteria for the symptomatic cohort, Model for the Development of Early Knee Osteoarthritis (MoDEKO), were: 1) pain, aching, or discomfort in/around the knee on most days of the month at any time in the past; 2) pain, aching or discomfort in/around the knee in the past 12 months. In the asymptomatic cohort, participants responded no to both knee pain questions. All participants received a standardized knee exam, fixed flexion knee radiographs and MRI, and completed a comprehensive questionnaire, which included a detailed lifetime occupational history of activity level (5 levels) and knee bending/kneeling activities (3 levels) for each occupation held. Self-reported COPL was calculated by multiplying the number of years in each occupation by the activity level and by the knee bending within that occupation, then summing all occupations. COPL was then grouped into quartiles (QCOPL). SOA was defined by the Kellgren Lawrence x-ray grade > 2, plus the presence of knee pain. MRI-OA was defined using a novel definition by Hunter et al1which required either both group A features: osteophyte formation and full thickness cartilage loss; or one group A and two group B features: bone marrow lesion or cyst, meniscal subluxation or tear, partial cartilage loss, or bone attrition. Weighted analysis was done using logistic regression to examine the association between QCOPL and the presence of SOA and MRI-OA, respectively, after adjusting for age, sex, body mass index, and two-way interactions.
Results: Participants (women=167, men=160) were on average 58.5 (SD=11.0) years old with a BMI of 26.3 (SD=4.7). Of those, 102 (31.2%) participants had SOA. A monotonic statistically significant relationship was found between QCOPL and SOA with adjusted odds ratio (OR) of 8.16 (95% CI = 1.89, 35.27) for QCOPL 4 (highest) vs. QCOPL 1 (lowest), and 5.73 (95% CI= 1.36, 24.12) for QCOPL 3 vs. 1. A total of 131(40.1%) participants had MRI-OA. Adjusted OR were also monotonic and statistically significant: QCOPL 4 vs. 1 (OR= 9.54; 95% CI = 2.65, 34.27); QCOPL 3 vs. 1 (OR= 9.04; 95% CI = 2.65, 30.88); QCOPL 2 vs. 1 (OR = 7.18; 95% CI = 2.17, 23.70).
Conclusion: COPL is a significant risk factor for knee OA. A dose response relationship between COPL and both SOA and MRI-OA was found. MRI-OA is a new definition, which has potential to capture early structural disease in a way not previously quantified. Due to the nature of the cross-sectional study design, these results should be interpreted cautiously but provide evidence for further prospective, longitudinal studies.
(1) Hunter et al. Osteoarthritis and Cartilage 2011; 19(8):963-969.
A. M. Ezzat,
E. C. Sayre,
L. C. Li,
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ACR Meeting Abstracts - http://acrabstracts.org/abstract/cumulative-occupational-physical-load-as-risk-factor-for-knee-osteoarthritis/