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Occupational physical demands, knee bending, and knee osteoarthritis: results from the Framingham Study
D T Felson1, M T Hannan, A Naimark
1Department of Medicine, University Hospital, Boston, MA.
Insights
Occupational joint use, particularly jobs involving knee bending and physical demands, significantly increases the risk of osteoarthritis (OA) in men. This longitudinal study highlights a key occupational risk factor for knee OA development.
Area of Science:
- Occupational Health
- Rheumatology
- Epidemiology
Background:
- Osteoarthritis (OA) is a prevalent degenerative joint disease.
- Occupational factors are increasingly recognized as contributors to OA development.
- Longitudinal data on the impact of specific job demands on OA is limited.
Purpose of the Study:
- To investigate the longitudinal association between occupational joint use and the incidence of knee osteoarthritis (OA).
- To identify specific job characteristics, such as physical demand and knee bending, associated with OA risk.
- To analyze these associations in a large, long-term cohort study.
Main Methods:
- Utilized data from the Framingham Heart Study cohort, followed over 40 years.
- Assessed occupational status and job characteristics (physical demand, knee bending) early in the study.
- Evaluated knee OA using weight-bearing radiographs in later life (mean age 73).
- Employed logistic regression to adjust for covariates like age, BMI, and smoking history.
Main Results:
- Men in occupations requiring both knee bending and at least medium physical demands showed significantly higher rates of radiographic knee OA (43.4% vs. 26.8%).
- These men also had increased rates of severe radiographic OA and bilateral OA.
- No significant association was found between occupational factors and symptomatic knee OA in men.
- Few women held physically demanding jobs or jobs involving knee bending, and these were not associated with later OA.
Conclusions:
- Occupations combining knee bending and significant physical demands represent a substantial risk factor for developing radiographic knee OA in men.
- These findings underscore the importance of considering occupational exposures in OA prevention strategies.
- Further research may explore targeted interventions for high-risk occupations.
Abstract:
We sought to assess occupational joint use and osteoarthritis (OA) longitudinally in a large population with multiple occupations. Subjects were members of the Framingham Heart Study cohort followed over 40 years with occupational status assessed at the beginning of the Heart Study [from Examination 1 (1948-51) through Examination 6 (1958-61)] and knee OA assessed by weight bearing knee radiograph at Examination 18 (1983-85) when mean age of subjects was 73 years. Each subject's job was characterized by its level of physical demand and whether the job was associated with knee bending. Odds ratios (OR) testing the association of job demand with OA were adjusted by logistic regression for age, body mass, knee injury history, smoking, and educational level. Men whose jobs required knee bending and at least medium physical demands had higher rates of later radiographic knee OA (at least definite osteophytes) than men whose jobs required neither (43.4 vs 26.8%; OR of OA = 2.22, 95% CI 1.38, 3.58). Rates of severe radiographic OA (osteophytes and joint space narrowing) and of bilateral radiographic OA were also significantly increased in these men. Few women had jobs requiring knee bending or that were physically demanding and these jobs were generally unassociated with later radiographic OA. Only a small number of men (n = 28) had symptomatic knee OA, and we could not confirm that it was associated with occupation in men. Thus, among men, occupations which combine knee bending and physical demands may be an important cause of radiographic OA.