At first, the problem was easily put right by a single visit to an osteopath. But five years and three pregnancies later, I had endured more acute episodes than I could count and a day rarely passed without pain.
Otherwise fit and energetic, I could not lift my kids on to a swing without risking three days in bed. Back sufferers are bores: they live in fear of triggering the pain and, cruel but true, the fear itself becomes a trigger. I was habitually tense, careful, resentfully resigned to a self- protective, no-fun-and-games attitude. At 32, I felt old.
Orthopaedic surgeons scanned and prodded, but concluded that an operation was not appropriate. They told me I had a scoliosis - an ominous, medieval torture chamber sort of word - and that it "might stabilise".
In fact, scoliosis (curvature and twisting of the spine) affects about one in 250 of the population. My own is mild-ish, idiopathic (an expert's word, meaning the experts are not sure why it developed) and functional (caused by the muscles). Pitifully weak back and stomach muscles - the results of pregnancy, as well as years of maniacally self-protective behaviour - had not helped.
I tried acupuncture, yoga, hypnotherapy, the Alexander technique - all positive, all helpful, but only for about three weeks. The amount of money I had chucked at my spine by now was becoming depressing.
Lesley Ackland was the third Pilates teacher I had tried. There are several in London, but I had been put off by expensive fees, over-chic studios, precious and competitive women in mint leotards, and teachers who taught without making eye contact, urging me to "relax into the pain" - in other words, to pull myself together and get on with it.
A friend and fellow-sufferer was appalled. "Pilates should not hurt," he said, and gave me Lesley's phone number.
From the start, she was encouragingly uncompromising. "You've got to be able to use your body confidently and spontaneously," she told me. "What if you're in a restaurant and you drop your napkin? You've got to be able to pick it up just like that, without thinking."
She promised to help realign my body, relax my posture and enable me to move with greater spontaneity. "Apart from anything else," she said, "a scoliosis isn't glamorous." I liked the way she was thinking.
Pilates was developed by Joseph Pilates, a German PE instructor and gymnast whose interest in exercise as a physical corrective grew out of the muscular misalignment which he himself suffered from childhood. A system of gentle physical exercise, it strengthens muscles and realigns the body with minimal risk of injury. I could never have exercised in a standard gym - I was too weak and my back too vulnerable - but many Pilates exercises are done flat on your back or with the back supported, to give confidence that they will not hurt.
As in a standard gym, repetitive movements are carried out on various pieces of equipment, many of them involving weights. Each individual follows a different, personally tailored programme and new exercises are added all the time.
Lesley Ackland is remedial exercise consultant to the London City Ballet. She is trained in Pilates-based techniques and has developed updated versions of the original exercises which she teaches in her studio.
The first thing she did was to devise a mobility and strengthening programme and a general fitness routine, with emphasis on the abdomen, lower back and legs, to tackle my upper back scoliosis. I agreed to exercise three times a week - a big commitment, but one that has since paid off. Work was also begun on my feet and lower legs which were hopelessly misaligned and responsible for a gait that did not help my back.
In any one session, I would do stomach and back-strengthening on a mat on the floor, arm weights on a "barrel" and legwork with my feet in sprung straps or in the "plie machine" - a daunting-looking contraption on which I have to lie down and push away with my feet. I also exercise with a tennis ball, a slope, a "wobble board" and a large rubber physiotherapy ball.
My progress, at first exhilaratingly swift, has since slowed to a realistic, but encouraging rate, but has never stopped. There are occasional setbacks (especially when a new movement has been introduced and my body reluctantly adapts), but I am straighter than I ever thought possible, my acute episodes are further and further apart and most days I am without pain.
It is bewildering that no back specialist, and few of the osteopaths I have encountered, have heard of the Pilates method. For years I was sent home from my scans and tests with nothing but a sense of hopelessness.
A year later, I cannot say I am cured but my problem has changed in a way I find both lasting and acceptable. I will probably never go out of my way to lift chubby toddlers, but I can walk for miles, run for a bus, sit and play with Lego on the floor, and stand at a party without suffering the next day.
And next time you see my napkin flutter to the floor, please do not pick it up for me.
For information on Pilates treatment, contact Lesley Ackland on 0171- 379 6043.