Changing concepts in skeletal physiology: Wolff's Law, the Mechanostat, and the "Utah Paradigm"

According to the Utah paradigm of skeletal physiology: (1) mechanical forces on skeletons generate signals in skeletal organs that control the biologic mechanisms that determine the architecture and strength of those organs, (2) these occur in ways that let the organs endure their voluntary mechanical usage for life without hurting or breaking, (3) to work properly, these mechanisms need nonmechanical factors (hormones, vitamins, calcium, genes, cytokines, etc.), (4) only mechanical factors can guide those mechanisms in time and anatomical space, (5) this arrangement determines skeletal health and disorders can cause or help to cause numerous disorders of skeletal and extraskeletal organs (the collagenous tissue in ligaments and tendons also forms a part of extraskeletal organs). Accumulated evidence now strongly supports these features of the Utah paradigm, which supplements a 1960 paradigm. It incites reassessment of some former ideas about skeletal physiology and disease. Some controversies ensue that will take time to resolve. After they are resolved, skeletal science, medicine, and surgery should be significantly better than before and different in unforeseeable respects as well. Am. J. Hum. Biol. 10:599-605, 1998. © 1998 Wiley-Liss, Inc.