Background/Purpose: While recommended levels of physical activity associated with reducing the risk of poor health outcomes are well known, it is unclear what minimal level of walking is associated with functional benchmarks specific to older adults.  The purpose of this study was to examine the minimal number of steps/day associated with walking at a community level gait speed in older adults with or at high risk of knee osteoarthritis (OA).

Methods:   The Multicenter Osteoarthritis Study (MOST) is an NIH funded longitudinal study of older men and women who have or are at high risk for knee OA.  Participants at the 60-month visit wore a StepWatch Activity Monitor to record walking behavior over 7 days.  Usual gait speed (m/s) during a 20 meter walk was determined at the same clinic visit.  Walking behavior (steps/day) that best discriminated a gait speed of ≥1.2 m/s (speed needed to cross the street) was determined using a Receiver Operator Curve (ROC).  Sensitivity, specificity, and positive predictive value (PPV) was calculated to quantify how well the identified steps/day predicted walking at least 1.2 m/s.

Results:   Among 1,757 participants considered (67 ± 8 yrs, BMI 31 ± 6 kg/m², female 59%), mean walking behavior was 7,094 ± 2,917 steps/day [range 640 – 21,593] and mean gait speed was 1.22 m/s ± 0.21 [range 0.4 – 2.1].  Walking at least 6,500 steps/day discriminated meeting a gait speed of ≥1.2 m/s (sensitivity = 70%, specificity = 64%, PPV = 71%).

Conclusion:   Most older adults with or at high risk of knee OA who walk at least 6,500 steps/day have gait speeds associated with walking in the community.  While further confirmation is needed, at present clinicians may consider setting a goal of 6,500 steps/day as a minimal level of walking for older adults with or at high risk of knee OA.