Factors that modify the association between knee pain and mobility limitation in older women: the Women's Health and Aging Study

Objective-To investigate the influence of pain severity, knee extensor musc le weakness, obesity, depression, and activity on the association between r ecent knee pain and limitation of usual and fast paced walking, and ability to rise from a chair. Methods-A cross sectional analysis of 769 older women (mean age 77.8, range 65-101) with physical disability, but no severe cognitive impairment. Seve rity of knee pain in the past month was classified as none, moderate, or se vere. Mobility was measured using timed performance tests. Results-The prevalence of recent knee pain was 53% (408/769). One third of the women with pain reported it to be severe. In general, knee pain was onl y significantly associated with limited mobility if severe. Obesity, activi ty and, to a lesser extent, depression intensified the effects of pain. Kne e extensor weakness did not. Obesity was a distinctive risk factor in that it substantially increased the risk of mobility limitation, but only in wom en with pain. In women who had severe pain, activity (walking more than thr ee city blocks in the past week) increased the risk of walking disability m ore than inactivity. Depression had a minor, but statistically significant effect on walking ability, but not the ability to rise hom a chair. Conclusion-In older women with recent knee pain, a high pain severity score , obesity, and activity are important factors that increase the risk of mob ility limitation.