Relationship between frequent knee pain, obesity, and gait speed in older adults: data from the Osteoarthritis Initiative.

BACKGROUND Knee pain (KP) causes gait difficulties in older adults and is associated with slow gait speed (GS). Obesity has negative effects on health. GS is an important indicator of health, well-being, and mean life span in older adults and is a strong predictor of future disability and mortality. The relationship between frequent KP, obesity, and GS in older adults remains unclear. Therefore, the present study aimed at examining the relationship between baseline frequent KP and obesity status on GS over time. We hypothesized that frequent KP, obesity, or both would be associated with decreased GS over time. METHODS The data from the Osteoarthritis Initiative were used for this 6-year longitudinal cohort study. We studied 3,118 adults aged between 45 years and 79 years. We grouped the participants into the following four categories according to KP frequency and obesity status at baseline: 1) no KP and nonobese, 2) frequent KP and nonobese, 3) no KP and obese, and 4) frequent KP and obese. GS measurements were based on a 20 m walking test timed using a stopwatch; testing was performed at baseline and over a 6-year follow-up period. Walk pace (m/sec) was calculated as the average pace over two trials conducted at clinic visits. General linear mixed models were used to examine the relationships between frequent KP, obesity, and GS. RESULTS After adjusting for all covariates, at baseline, all the nonobese group with frequent KP (β=-0.06, 95% confidence interval [CI]: -0.07 to -0.04), the obese group with no KP (β=-0.07, 95% CI: -0.1 to -0.04), and the obese group with frequent KP (β=-0.08, 95% CI: -0.1 to -0.05) exhibited decreased GS compared with the nonobese and no KP group. However, the associations between frequent KP, obesity, and GS over time were not statistically significant. CONCLUSION Frequent KP alone, obesity alone, and the combination of frequent KP and obesity were all associated with decreased GS in older adults. These associations did not change in any of the groups longitudinally; as such, the slopes corresponding to the data remained unchanged.