Longitudinal study of knee pain amongst workers in the Cultural and Psychosocial Influences on Disability (CUPID) study

Background

Knee pain is common in the general population, increasingly so with age. It causes substantial disability which can lead to premature exit from the workforce. Current epidemiological data on knee pain prevalence in working-age populations are limited, particularly concerning the interplay of occupational, psychosocial, and cultural factors. To address this, in a large group of workers, we examined the prevalence of knee pain longitudinally, its relationship with pain at other sites and personal and occupational risk factors for pain at follow-up.

Methods

Data came from the CUPID study, a cohort study including people aged 20–59 years at work from 18 countries in broadly three types of occupations: office work, nurses and manual workers. Baseline data were collected on knee pain, pain at other anatomical sites, occupational characteristics and psychosocial aspects of work. Follow-up information about knee pain was obtained approximately a year later. Descriptive statistics were used to describe knee pain prevalence and characteristics as well as persistence. Poisson regression was used to explore baseline factors in relation to knee pain, and disabling knee pain, at follow-up.

Results

In total 9,161 workers provided baseline and follow-up data, amongst whom 28% reported knee pain in the past year and 21% knee pain in the past month at baseline. 79% of workers with knee pain reported disability. The prevalence increased with age and was higher among women. Only 8% of workers with knee pain had single-site pain. There was wide variation in the prevalence rates reported amongst workers even doing broadly similar work. Psychosocial and occupational work demands predicted knee pain at follow-up, as did poorer mental health and somatisation but the highest effect size was found amongst people reporting a high number of painful sites at baseline (PRR: 2.06,95%CI: 1.78–2.39).

Conclusions

Knee pain is prevalent in the workforce, even at younger ages. It is commonly persistent and disabling. Given its link with work disability, the emphasis needs to be on prevention and both mechanical and psychosocial exposures at work are implicated. However, like low back pain, other factors appear to be important, particularly pain at other sites.