 Study hypotheses: 1 Ankle motion during distraction will result in clinically significant improvements in Ankle Osteoarthritis Scale scores, SF-36 scores, and improved cartilage thickness distribution over the habitually most heavily loaded portion of the articular surface, as compared to the use of distraction without ankle motion. 2a Ankles with low geometric surface irregularity and greater range of motion will have better preservation of neo-chondroid tissue increased normalized cartilage thickness and reduced longitudinal compressive strain in the habitually heavily regions of the articular surface than those with high surface irregularity. 2b Low geometric surface irregularity and greater range of motion will have reduced habitual focal or regional contact stress elevation. 3 Joints that have better improvements in Ankle Osteoarthritis Scale scores and improved cartilage thickness distribution over habitually heavily loaded portion of the articular surface will have improved normalization of synovial fluid markers of biosyntheticdegradative activity and oxidative stress. 