Wolff's Law "Applied"

A simple illustration of bone's adaptability according to Wolff's theories. Keep in mind, Wolff was only working with gross specimens of bone, and he predated what we now know about bone remodeling. The drawings above (based on the tibia) show two stressors acting on the bone, compression (C) and tension (T). The black arrows denote the net direction of a load force applied (by the animal's weight) to the bone. Note, changes in bone (red) demonstrate cortical bone modeling that would be seen in a growing animal as the load on the tibia is increased from X to 2X. The cortices under compression increase in width (density of bone also likely increases), while bone under tension is removed for greater flexibility. Bone modeling in this illustration is assuming the bone can adapt to the increased load without fracture. For this example, increasing the load on the bone beyond 2X would eventually lead to a fracture, likely along one of the tension surfaces. Interestingly, while the compressed cortical bone is increasing to support the extra load, the compressive surface will also eventually become "unhealthy" by the accumulation of unrepaired microcracks/microfractures.