Fig. 1. Force equilibrium. The three forces acting on the hip joint balance one another to keep the body in equilibrium. These forces are the abductor muscle force(a), the weight of the upper body(t), and the hip joint reaction force(r). The polygon of forces froms a closed figure with no resultant.

Fig. 2. Left, A free-body diagram of the hip of a man standing on his right leg; the body and the left leg Right, A force triangle may be constructed to determine the joint-reaction force Fj.

Fig. 3. The combination of bending and compressive stress in the femoral neck acts to decrease the tensile stress in the lateral aspect of the neck.

Fig. 4. Diagram of stress tensor showing the 3 normal stress ( ) and 3 shear stress (r)

Fig. 5. (Left) Finire element mesh and three loading conditions used to emulate skeletogenesis and bone remodeling in the normal proximal femur. (Center) Computational emulations of bone density distribution resulting after one-time increment(t=1a); and (Right) after thirty time increments(t=30a). Adapted from Beaupre et al.,(1990b) and Orr(1990).

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