OBJECTIVE To determine if different foot orthoses have a similar effect on foot kinematics in subjects with ankle osteoarthritis (OA) when walking on various ground conditions. METHODS Within-subject comparisons study. METHODS Biomechanics research laboratory. METHODS Thirteen subjects with unilateral ankle OA. METHODS Custom-made ankle-foot orthosis (AFO), rigid hindfoot orthosis (HFO-R), and articulated hindfoot orthosis (HFO-A) were used by subjects when walking on level, ascending and descending ramp, and side-slope conditions. METHODS The range of motion of the hindfoot (calcaneus relative to tibia) and forefoot (metatarsal relative to calcaneus) was measured using an 8-camera motion analysis system. RESULTS The AFO and HFO-R provided the best sagittal plane hindfoot motion restriction over all ground conditions (P<.001). The HFO-R allowed the greatest sagittal plane forefoot motion when walking over level (P=.01) and side-slope (P<.02) conditions, the greatest frontal plane forefoot motion walking down the ramp (P=.003), and the greatest transverse plane forefoot motion when walking over level (P=.011) and ramp-ascending conditions (P=.005). The HFO-A restricted motion of the unaffected joint and did not effectively restrict hindfoot motion. CONCLUSIONS The HFO-R not only provides selective restriction to the ankle-hindfoot motion, but also allows sufficient forefoot motion compared with the AFO. We consider the HFO-R to be the best option of all tested orthoses for treating patients with ankle OA pain arising from ankle motion.