A 52-year-old quantity surveyor who has worked from a desk at home for six years has tripped four times in three weeks, twice on the same slightly raised paving slab he has walked over daily for years. He now holds the handrail on stairs, watches the pavement rather than where he is going, and has stopped cycling because he cannot trust the downstroke. It has been three weeks, and he thinks something was there for a week or two before the first trip. There is no pain at all — not in the leg, the back or the buttock — and there was no fall, twist, blow to the leg, surgery or change of footwear. He looks entirely well and apologises for wasting the appointment on clumsiness.