Have you noticed how quickly shoes suddenly become too uncomfortable/painful to wear? Under the heel (inside) there is a high chance that you will discover a hard moulded block of squares, reminds me of a waffle. After a few hours, days weeks you suddenly get pains in your heels. This is because the material above the 'waffle' the material that your heel stands on is wearing and weakening, the effect of your heel coming down on those uncomfortable squares gets more painful by the day.
I went to the doctor with a painful heel and she said it might be something like gout and gave me the most painful jab in the heel. Not so long after that I discovered what the real cause was!!
I recently called in on a shoe shop and ALL THE SHOES BUT ONE had this waffle in the heel, I could have even pushed my thumb right through one particular pair, the manager said "most shoes are like this nowadays". So next time your heel hurts, take a look inside the heel!