Osteoporosis

Osteoporosis is a bone remodelling imbalance, not a single disease event

Bone is continuously remodelled by osteoclasts, which resorb old bone, and osteoblasts, which lay down new bone, normally in tight balance. Osteoporosis develops whenever resorption outpaces formation for long enough: most commonly after the menopause, when falling oestrogen removes its restraint on osteoclast activity, but also with ageing, immobility, glucocorticoid use, and other secondary causes. Because the problem is a chronic net loss of bone rather than a discrete injury, osteoporosis itself is silent and painless: it only becomes apparent when the weakened bone fails.