ABERDEEN, UK—Nearly one in 10 new employees develop knee pain in the 2 years after they start working. Job stress and single-handed lifting are the two major risk factors, according to a prospective study in the March issue of the Annals of Rheumatic Diseases.¹ For more than half these workers, knee pain resulted in some disability or consultation with a physician.

The psychological and psychosocial factors in new-onset knee pain may open new avenues for prevention. "However, before we can hope to use this knowledge in trials of prevention, we first need to understand the mechanism by which these psychosocial factors are related to a high prevalence of knee and other musculoskeletal pains," conclude researchers led by Gareth T. Jones, MD, of the University of Aberdeen, in the UK.

More stress, more risk of knee pain

Dr. Jones and colleagues conducted the New Workers Study, a prospective cohort study of 859 newly employed workers  from 12 diverse occupational settings in England including firefighters, police, army officers, dentists, retail workers, nurses, and postal workers. All participants were free of knee pain at inception. Subjects were questioned about occupational mechanical factors, including manual handling and postural activities and occupational physical environment. They were also asked about job demands (work pace, stress/worry, whether they found their job boring), job control (whether they felt able to make their own decisions or had the chance to learn new things), job support (from colleagues and supervisors), and overall job satisfaction. General psychological distress was assessed using the General Health Questionnaire. Participants were followed up after 12 and 24 months.

Over the 2-year follow-up period, there were 108 cases of new-onset knee pain. During that time, mechanical load, postural factors, psychological distress, and workplace psychosocial factors all influenced the risk of new-onset knee pain. Workers who lifted or carried weights in one hand increased their risk of developing knee pain by 60%, the study found.

The greater the psychosocial distress at work, the greater the risk of knee pain. Specifically, patients who said their job was monotonous or had little control at work were 70% more likely to experience new-onset knee pain than their counterparts who did not find their job tedious or who had a sense of control, respectively. Workers who were seldom able to learn new things on the job were 80% more likely to develop knee pain than colleagues who were learning at work, the study showed.

Table: Factors That Predict Development of Knee Pain

Predictor of New Knee Pain