Righting tibial retroversion : a functional and ontogenetic analysis

Tibial retroversion, or the posterior angulation of the tibial plateau relative to the diaphysis, has been tentatively linked to several behaviors in anthropological literature. While a large body of work, dating as far back as the late 1800's, has linked this morphology to squatting postures, this association is primarily from comparative studies of human groups as opposed to more controlled studies in populations knowns to squat. Other scholars have suggested that retroversion is related to overall robusticity or more explicitly, extensor muscle moment arm development. This research attempts to clarify the underlying etiology of tibial retroversion by analyzing it in an explicitly ontogenetic and functional perspective. First, this analysis explored age and population-level variation in tibial retroversion. Second, the relationship between tibial retroversion and long bone strength via cross-sectional geometric properties was evaluated. This study used a large cross-sectional sample of immature modern human remains from seven historical and archaeological osteology collections that vary in origin and activity patterns. Results of this analysis indicate that there is no relationship between tibial retroversion and age after the first six months of life, while populations and subsistence strategies differ in their magnitude of retroversion. In addition, there is no relationship between tibial retroversion and size-standardized cross-sectional geometric properties, implying that variation in this feature is not purely a function of loading and activity levels. The lack of association with age and robusticity suggests that additional research is needed to shed light on whether this morphology is associated with squatting or other functional correlates.