Physical Workload and the Risk of Severe Knee Osteoarthritis

Objectives: This study investigated the impact of physical workload on the risk of severe knee osteoarthritis (OA) leading to knee arthroplasty.

Methods: In this case-referent study, the cases were 55- to 75-year-old men (N=55) and women (N=226) who had undergone their first knee arthroplasty operation for primary knee OA in the Kuopio University Hospital in 1992-1993. The referents (N=524) were from the same source population and were matched with the cases for age and gender. Information on explanatory variables was obtained by a computer-assisted telephone interview. Exposure was assessed up to 49 years of age.

Results: After adjustment for body mass index, knee injury and leisure-time physical activity, an increased relative risk of knee OA was found for a history of high physical workload. The odds ratio (OR) was 1.53 [95% confidence interval (95% CI) 0.42-5.56] for the men and 2.03 (95% CI 1.03-3.99) for the women as compared with those with low physical workload. With respect to generic risk factors, climbing already at a medium level of exposure was associated with an increased risk of knee OA among the men (OR 3.06, 95% CI 1.25-7.46) and kneeling and squatting was a risk factor for both genders. Of the different trades, agriculture, forestry, fishing, transportation, and traffic showed the highest risks of knee OA.

Conclusions: The results of this study agree with the hypotheses that heavy physical loading increases the risk of knee OA and that cumulative physical stress has a deleterious effect on the knee joint.