Arthritis care & research. 2014;66(9):1328-1336.
Background: Physical activity is recommended to mitigate functional limitations associated
with knee osteoarthritis (OA). However, it is unclear whether walking on its own protects
against the development of functional limitation. Methods: Walking over 7 days was
objectively measured as steps/day within a cohort of people with or at risk of knee
OA from the Multicenter Osteoarthritis Study. Incident functional limitation over
two years was defined by performance-based (gait speed â‰¤ 1.0 m/s) and self-report
(WOMAC physical function â‰¥ 28/68) measures. We evaluated the association of steps/day
at baseline with developing functional limitation two years later by calculating risk
ratios adjusted for potential confounders. The number of steps/day that best distinguished
risk for developing functional limitation was estimated from the maximum distance
from chance on Receiver Operator Characteristic curves. Results: Among 1788 participants
(mean age 67, mean BMI 31 kg/m(2) , female 60%), each additional 1000 steps/day was
associated with a 16% and 18% reduction in incident functional limitation by performance-based
and self-report measures, respectively. Walking < 6000 and < 5900 steps/day were the
best thresholds to distinguish incident functional limitation by performance-based
(67.3%/71.8% [sensitivity/specificity]) and self-report (58.7%/68.9%) measures, respectively.
Conclusions: More walking was associated with less risk of functional limitation over
two years. Walking â‰¥ 6000 steps/day provides a preliminary estimate of the level of
walking activity to protect against developing functional limitation in people with
or at risk of knee OA. Â© 2014 American College of Rheumatology.