With my co-parent away at a conference, every last nanosecond of the week ahead had been earmarked - children to ferry, deadlines to meet. Tired, so tired. Reaching for a carton of juice, standing on the kitchen work-surface (why was such a staple kept so high up? Because that's where it's always been) I lost my balance and crashed to the floor.

Everyone has their own hierarchy of fears. Breaking a leg was never prominent in mine. Cancer? Most certainly. Heart attack? Quite possibly. But to a hypochondriac of my rank a fracture was much too banal to win a place on my fret-list, especially as I've always avoided any leisure activity that entailed either leaving the ground or developing too close a relationship with it.

That same moment in which I suffered a triple fracture of the tibia, just under the knee-joint (ouch!), revealed what most of us expend a lot of energy denying: that the line between independence and dependence is very faint indeed (except once you're firmly in the second category). Of course a decent amount of denial is probably essential: we need to turn that faint line into a ravine, for sanity's sake, although if another person tells me that most accidents happen in the home I may not be able to stop myself from deliberately inflicting one more.

Two weeks in hospital - strong painkillers and intense bonds. One day a gaunt woman, circa 101, arrives in the bed opposite. Slipping in and out of lucidity, she has to be fed - great globules of food are shovelled into her mouth by a kind but abstracted ward assistant. At night she repeats a (phone?) number so obsessively until I feel as though I'm dementing too.

All I did was fall in my kitchen, so why do I need this terrible harbinger of what life might eventually bring? I try to cordon off this woman until finally I get it: the task is to accept one's own and other people's frailties with compassion.

But it's hard: back at home I feel quite abject. Nine weeks without a bath - Barbara, a NHS-supplied carer, helps me wash in bed instead. I'm not only a disabled mother now, I feel, but also disabled as a mother, and must watch while other people do my usual tasks - differently. I also have to learn not to make demands, to husband my requests into manageable blocks so as not to put extra pressure on those replacing me. Now I know why they call us patients.

But three things become clearer. One is that powerlessness may be the hardest state for modern, middle-class citizens to tolerate - it returns you so painfully to infancy. The whole culture today is about empowering this and empowering that: tougher by far to accept limitation and weakness, incapacity and dependency, yet they're inescapable aspects of the human condition too. We feminists have something to answer for in failing, too much of the time, to acknowledge this.

Then, when I finally ventured out on crutches, I experienced what for years I'd only written about: how inhospitable public space is to any but the absolutely fit. The pavements are like a 3D Ordnance Survey map of the Lake District, each step an encounter with a scrag, fell or valley. Vast, heavy fire-doors more befitting a Florentine palazzo grace ordinary buildings, even their disabled loos. Only the camaraderie of the impeded - shared smiles and remarks - provided relief. I admired afresh my always-travelling friend with brittle bones for triumphing - not over his disease, but over the able-bodied and the obstacles they place in his way.

But above all I learned the value of kindness: from fellow parents (the roast chicken quietly delivered, the endless lifts and invitations to sleepovers - the more harried and nannyless they were, the more help they offered), from friends (the foot massage and ferrying), my children (my lippy teenager suddenly - if temporarily - a picture of supportive maturity), and my husband (in effect a single parent, but never once berating me for my foolish fall, as I would have were our positions reversed). I haven't been this kind to others, and resolve to be.

Seven months and a lot of brilliant physio later, I'm walking, driving and even beginning to dance once more, and savouring every step. But never again will I feel so invulnerable - and that, surely, is good.