Intraindividual variation in the cross‐sectional geometry of the first metatarsal, femur, and tibia

Abstract Objectives The examination of cross‐sectional properties (CSP) of long bones can inform about differential activity patterns and levels of mobility. Typically, these analyses have focused on the femur and tibia, but metatarsals might also be informative. This study examines femora, tibiae, and first metatarsals to evaluate the relationships between long bone CSP within the lower limb and how this might improve our interpretations of metatarsal variability. Materials and Methods The study includes protohistoric Andaman Islanders ( n = 26) and Later Stone Age (LSA) Southern Africans ( n = 25) from approximately 10,000–500 BP. Skeletal data were acquired from past studies of these groups. Correlations were used to evaluate the relationships between CSP of lower limb bones within individuals. Principal component analyses were used to evaluate how each lower limb bone contributed to variation in CSP among individuals. Results The correlations between the CSP in the femur and tibia were always strong, but the correlations with the first metatarsal are variable. Variation in femoral loading largely drove PCAs, with less influence by the first metatarsal, or loading in the opposite direction. Discussion The femur and tibia experience similar patterns of mechanical loading, specifically in compression and tension, but the first metatarsal does not reflect the same biomechanical patterns as the femur and tibia. Similarly, the first metatarsal often drove variation in the opposite direction as the femur, indicating differences in the mechanical loading pattern between the two bones.