Figure 6. Orthogonal arrangements of trabeculae usually reflect a highly consistent loading regime experienced by a bone.

(A) Sagittal section through the calcaneum of a cow, with the pull of the Achilles tendon on the distal end indicated by the arrow. (B) A force applied to the free end of a cantilever beam is comparable to the loading regime experienced by the cow calcaneum during locomotion. The bending of the cantilever beam produces principal stress trajectories that are very similar to the overall arrangement of trabeculae in the calcaneum (solid lines are trajectories of compressive stress; dashed lines are trajectories of tensile stress). Since the calcaneum is only loaded in this fashion, the two systems of trabeculae (one curving from up, one curving down) tend to intersect at right angles.