ABSTRACT
The phenomenon of bone adaptation has been known for more than a century, since the original studies of Roux (Roux, 1881) and Wolff (Wolff, 1892). Mechanical adaptation of bone is the process whereby living bone adapts its mass and structure to prevailing mechanical usage, to obtain a higher efficiency of load bearing. Adaptation will improve an individual animal’s survival chance, because bone is not only hard, but also heavy. Too much of it is probably as bad as too little, leading either to uneconomic energy consumption during movement (for too high bone mass) or to an enhanced fracture risk (for too low bone mass). This readily explains the usefulness of mechanical adaptation, even if how it is performed is not understood. In the time of Roux and Wolff it also became apparent that bone is a
tissue
, made by cells and degraded by cells. The terms
osteocyte
,
osteoblast
, and
osteoclast
stem from that same time period. The mechanical function of that tissue is performed by the lifeless material between the cells, the
extracellular mineralized matrix. The role of the cells is to make and degrade that matrix, in relation to mechanical demands.
