Femoral and tibial diaphyseal geometry has frequently been used to evaluate mobility and other patterns of physical activity in past populations. The high antero-posterior (A-P) to medio-lateral (M-L) bending rigidity ratio (IX/IY) typical of many hunter-gatherer femora, for instance, may reflect mechanical loads associated with long distance travel. The possible confounding effect of physical terrain on lower limb diaphyseal morphology is rarely evaluated. This study investigated the possible effect of terrain on lower limb shape ratios (IX/IY) and bending and torsional strength (ZP) in adult skeletons from Europe, North America, Africa, and Asia, covering a time span from around 30,000 BP to the present. Midshaft femoral and tibial cross-sectional geometric properties for 3515 individuals were gathered from databases kindly provided by researchers. Geographic coordinates were found for each archaeological site. Local terrain for each site was quantified with ArcGIS 10 mapping software using USGS elevation data, and characterized as flat, hilly, or mountainous. Analysis of variance shows significant differences (pP) of both femoral and tibial midshaft among the three terrain categories, with more A-P oriented diaphyseal shapes and greater strength in hilly and mountainous groups, even after correcting for the effect of subsistence on these cross-sectional properties. These results suggest that terrain needs to be taken into account in analyses of lower limb diaphyseal structure and mobility. Latitude and coastal proximity were also investigated as possible biogeographic factors in the morphology of lower limb diaphyses.