Knee osteoarthrosis in relation to physical workload and lifestyle factors : epidemiological studies

Abstract

This thesis investigates the relationship between physical workload, sports, and lifestyle factors and the development of knee osteoarthrosis (OA) in ex-elite athletes, in men and women in the population, and in physical education (PE) teachers. It is based on four investigations: two cohort studies, one population-based case-referent study, and one field study.

In a cohort study of 114 male ex-elite athletes in track-and-field, and 355 referents from the population, the aim was to investigate if musculoskeletal dysfunctions, especially OA in knees and hips were more common. The results show that hip OA was more common among the ex-elite athletes (PR 3.6, 95% CI 1.4-9.3), and probably also knee OA (PR 2.8, 95% CI 0.7-11). The ex-elite athletes estimated their present general health to be better, they were more active in fitness activities, and were less overweight than the referents.

A case-referent study of 625 men and women who had had knee prosthesis surgery and referents from the population aimed to investigate risk factors for severe knee OA. The strongest risk factor was overweight (OR men 3.9, 95% CI 2.3-6.4, women 9.2, 95% CI 5.3-16.0). Forestry and construction workers, and female and male farmers had an increased relative risk of severe knee OA compared with the referents. Lifts, jumps, kneeling, squatting, and vibrations significantly increased the odds ratios two or three-fold for men. Those women who had taken care of elderly relatives or handicapped children at home had an increased relative risk of severe knee OA (OR 2.2, 95% CI 1.3-3.6). Sports activities increased the relative risk for men, but sports exposure in women, both cases and referents, was very limited, and no increased risk could therefore be found. Moderate, daily physical activities, such as cycling and walking did not increase the relative risk among men and women.

In a cohort study of 571 female and male PE teachers and referents from the population, the aim was to investigate if PE teachers develop more OA in the knees and hips, and other musculoskeletal disorders. The results show that men and women who had been working as PE teachers 10 years or more had a higher prevalence of knee OA compared with the population controls (PR men 2.8, 95% CI 1.6-4.8, women 3.2, 95% CI 1.8-5.5). They also had to change jobs more often due to knee dysfunction. There was an increased prevalence of hip OA for the female PE teachers. The PE teachers reported a better health status, and fewer serious diseases than the population referents. They were also less overweight, had a considerably higher lifelong sports exposure, and smoked less.

In a field study, physical load exposure was monitored during entire workdays in thirty female and male PE teachers. The measurements were performed with equipment attached to the body, or systematic registrations. The results indicate that PE teachers have a considerable physical workload on the lower extremities in their everyday work and a high cardiovascular load in comparison with several other occupational groups.

In conclusion the studies demonstrate that overweight is the most important risk factor for symptomatic knee OA among men and women, and high physical load in work, home nursing, and high sports exposure are contributing factors.