Knee moment at work: validation of a questionnaire based on knee moment in working life

Classifications of occupations, such as those of the International Labor Organization, have previously been constructed with respect to the physical strain and joint moment to be expected in conjunction in a profession. To detect which occupational activities specifically induce high knee moments, we designed a questionnaire to analyze walking, knee bending, climbing of stairs and ladders, and jumping during three consecutive 15-year exposure periods in the professional lives of 920 consecutive residents [329 men with a mean age of 72 (range 47-96) and 561 women with a mean age of 77 (range 47-96)] drawn from the population records of the City of Malmö. The answers, classified into three categories with respect to knee joint moment, were compared with a classification of the occupations of all probands according to the same principles by three independent specialists in industrial hygiene. The two classifications showed a high degree of agreement, with Cramer's V ranging from 0.49 to 0.6, suggesting a co-variance with a common variable, i.e. the true work-related knee moment.