Osteoarthritis as a public health problem: the impact of developing knee pain on physical function in adults living in the community: (KNEST 3).

OBJECTIVES To determine the effect of newly developed knee pain on general health and physical function of people >or=50 yrs living in the community. METHODS Prospective cohort study of 3907 people aged 50+ registered with three general practices in North Staffordshire, in the UK. The main outcome measures were self-reported knee pain; general health and physical function as measured by the Short Form 36 (SF-36). RESULTS Of those with no knee pain at baseline, 24% (n = 501) reported it at follow-up. There was a steep decline in physical function in this group (mean fall in SF-36 score at follow-up 10.3 points) compared with the 1558 persons who had no knee pain at baseline or follow-up (mean fall 3.3). Those with knee pain at baseline whose pain had resolved at 3-yr follow-up (n = 409) showed only minor improvements in physical functioning scores at follow-up (mean improvement -1.3). CONCLUSIONS The onset of knee pain is associated with a substantial and persistent reduction of physical function in older adults living in the community. Since knee pain is common, and reduced physical function in mid to older ages is a strong predictor of future disability and dependency, effective prevention or early treatment of knee pain at these ages is likely to have a major influence on healthy ageing in the population.