1. Study Approval and Eligibility
IMPACT-P was approved by the Institutional Review Board of The Ohio State University. Participants were recruited from local medical clinics and arthritis foundation aquatics facilities. The full range of inclusion and exclusion criteria has been reported elsewhere [8]. To recruit a sample of older, community dwelling adults with symptomatic knee OA who had self-reported limitations in function but no serious medical contraindications to participation in center- or home-based PA of moderate intensity, the primary inclusion criteria were (a) years; (b) physician documented radiographic evidence of mild to moderate (II or III) tibiofemoral OA according to the Kellgren-Lawrence scale; (c) self-reported knee pain on most days of the month; (d) sedentary lifestyle with less than 20 min of structured exercise participation per week over the preceding 6 months; and (e) self-reported difficulty with common functions such as mobility. Primary exclusion criteria were (a) medical conditions that prohibited safe participation in an exercise program; (b) radiographic evidence of knee joint varus or valgus malalignment that, in the opinion of the physician, would make regular physical activity participation unsafe; (c) the inability to walk without a cane or other assistive devices; (d) OA severity > III on the Kellgren-Lawrence scale; or (e) the inability to complete the 12-month study or otherwise be compliant due to personal demands.