Summary
An elegant design stratagem would make its loads control the strength of an organ
intended to carry loads without breaking. Healthy load-bearing mammalian bones do
exactly that. Physiologists begin to understand how they do it, and this article reviews
some of the biological “machinery” responsible for it. Why? Because that machinery’s
features show what can cause age-related bone loss, how it occurs, how a long-overlooked
mechanism in bone marrow would contribute to it, why loss of whole-bone strength seems
more important than loss of bone ‘mass’, and why some absorptiometric indicators of whole-bone strength are unreliable. The machinery’s features also show why strong
muscles normally make strong bones, why persistently weak muscles normally make weak bones, and why loss of muscle strength usually causes a disuse-pattern osteopaenia.
Those things could question long-accepted ‘wisdom’, but four observations concern
that; (1) the questions concern what facts mean far more than the accuracy of the
facts, and the basic facts now seem pretty clear;
(2) this article must leave resolution of such questions, and of the devils that can
hide in the details, to other times, places and people;
(3) the plate tectonics story showed that better facts and ideas can change accepted
wisdom dramatically;
(4) and poor interdisciplinary communication delayed and still delays diffusion of
better facts and ideas to many skeletal science and clinical disciplines that needed
and need them.
Keywords
Biomechanics - gerontology - muscle - bone strength - anthropology
