Factors associated with change in pain and disability over time: a community-based prospective observational study of hip and knee osteoarthritis.

BACKGROUND

Hip and knee osteoarthritis are frequent causes of primary care consultations. They are considered slowly progressive disorders, often resulting in severe pain or disability and the need for joint replacements. There have been few longitudinal studies of progression to inform individual prognoses in primary care.

AIM: To describe the degree of progression and investigate predictors of change in hip or knee pain and disability.

DESIGN OF STUDY: Prospective community-based cohort.

SETTING

An age-sex stratified survey of 27 000 people registered with 40 general practices in Avon and Somerset yielded 2437 reporting hip and/or knee symptoms at baseline (1992-1994). A 25% random sample of 587 individuals was followed up between 1998 and 1999.

METHOD: Pain or disability was measured at baseline and followup using the New Zealand score. For the worst joint according to the New Zealand score at baseline, hip and knee problems were analysed separately. Regression models ascertained characteristics of nonresponders and factors associated with change in scores. Seven sociodemographic, seven comorbidity, and two healthcare utilisation variables were considered.

RESULTS

Generally pain and disability worsened over the 7 years, but 35% and 29% of those initially reporting hip and knee pain respectively had improved. Reporting "other health problems" was associated with greater deterioration for both hip and knee disease, as was cardiovascular morbidity for hip disease and lower social class, being retired, hypertension, and higher body mass index for knee disease. Deteriorations in scores were strongly associated with individuals consulting their GP about joint problems.

CONCLUSION

Osteoarthritis does not invariably deteriorate, but when it does social as well as biological factors appear to be important. These findings may aid outcome prediction. Future research on osteoarthritis should be conducted within a biopsychosocial rather than a purely biological paradigm.