The forces acting on the human calcaneus.

The forces acting on the human calcaneus are analysed for a static standing posture. An optimization procedure is invoked to solve the statically indeterminate set of forces which could arise from muscles, ligaments and reactions between the calcaneus and other bones and also the ground. Two alternative objective functions are investigated; that which returns no active muscle force is considered the more realistic, since electromyographic studies show that in static standing only minor muscle activity occurs to counteract body sway. This set of forces is then applied to the bone for finite element stress analysis to produce stress trajectories, which are then validated against both the trabecular configuration of the cancellous bone of the calcaneus and also the distribution of the orientations of the hydroxyapatite crystal major and minor axes.