Pedestrian road traffic injuries are a global concern with incidences ranging from 20–50 million each year. To support equitable and applicable research into pedestrian injuries, experimental studies must incorporate female and male samples of various ages and sizes. The objective of this study was to examine relationships between tibial biomechanical properties and sex, body size, and bone size to evaluate the role of each in understanding tibia response and identifying lower extremity injury thresholds, with a particular emphasis on the interaction between sex and size. Fifty-nine tibiae were impacted in a 6 m/s lateral-medial 4-point bending scenario to replicate a pedestrian-MVC impact to the leg. Overall, tibia structural properties were not significantly different between sexes in a dynamic 6 m/s blunt leg impact. No meaningful relationships between tibia structural properties and sex were observed. Trends demonstrated that dynamic tibia properties have more significant relationships with bone size than body size, when separated by sex. In localized loading (e.g., impact to pedestrian leg) bone size has stronger relationships with structural properties than body size. While this study was unable to conclusively identify variables contributing to variance in tibial response, the foundation for future research has been established.