I have one. Last night I posted because I had a sudden and agonising pain in the ball of my foot. It was like something broke. I went to out of hours and it all turns out to be a condition called 'Metatarsalgia'. It's nerve related and if simple treatments don't work, I'm looking at surgery that may cause complete numbness in the toes for life
Nothing caused it that we know of. I wear sketchers most of the time when not working. Don't even exercise much to cause it.