Circulation is difficult to observe directly. It is easy to observe indirectly, and the cheapest window onto it sits at the end of your legs. Blood has to travel further to reach the feet than anywhere else in the body, so when supply narrows the feet register it early — usually long before anything dramatic happens closer to the chest.
The symptom that gets blamed on footwear
Cold feet in a warm room, skin that has lost its colour, toenails that thicken and grow slowly, hair that stops growing on the toes, small cuts that take weeks rather than days to close. Individually each has an innocent explanation and usually the innocent explanation is correct. Together, and on one side more than the other, they describe a supply problem rather than a shoe problem.
The walking test nobody has to book
There is a pattern worth knowing by name: a cramping ache in the calf or thigh that arrives after a predictable distance, eases within a few minutes of standing still, and returns at roughly the same distance next time. The reliability is the point. Muscles that are being underfed complain when asked to work and stop complaining when the demand stops, and that on-off regularity is what separates it from an ordinary strain.
Numbness is a different messenger
Pins and needles, burning at night, or a patch that has gone quiet to touch are nerve signals rather than supply signals, and the two can travel together or separately. It matters because the loss of sensation removes the alarm: a blister or a stone in the shoe that would normally be intolerable can be walked on for a day without being noticed, and that is how a small injury becomes a slow one.
What raises the odds
Smoking, years of raised blood sugar, high blood pressure, high cholesterol and simple age all narrow arteries by the same unglamorous mechanism. None of them announce themselves in the feet on any particular day; they accumulate quietly and then the walking distance shortens by a street at a time, which is exactly the kind of change people adapt to instead of reporting.
Looking is most of the examination
A great deal of what a clinician does with feet is available to anyone with good light: compare the two sides, check the colour and temperature, look between the toes and under them, feel the pulses at the ankle and the top of the foot. Doing it once tells you very little. Doing it monthly tells you what has changed, and change is the only part that carries information.
What is worth mentioning, and what is worth mentioning sooner
Worth raising at a routine appointment: a walking distance that has shortened, one foot that is reliably colder or paler than the other, a nail or skin change that has been there for weeks. Worth raising promptly rather than waiting: a sore or blister that has not started healing after a fortnight, a foot that is painful at rest or at night, or any sudden change in colour or temperature. Feet are patient. That is precisely why they are worth checking on a schedule rather than when they finally hurt.