i) Microdamage is likely at a tolerable daily level and increases exponentially with age.

ii) Microcallus marks repair.

iii) Microcallus stiffens subchondral bone in the osteoarthritic femur and vertebral struts in the osteopenic spine.

iv) Repair may fail due to a decline in perception (via osteocytes?) or reaction (via remodelling).

v) Some areas are more at risk; immunohistochemically-defined matrix domains differ in macromolecular composition and also in the presence of Sharpey’s fibres, influencing response to stimuli and remodelling.

vi) Fractured axial, compression-resistant trabeculae stimulate microcallus more readily than do cross-strut, tensile trabeculae.