My patients often come into the office with a common complaint. They feel like they are walking on rocks. This can be the case for a number of reasons for some, it is because of a deep callus on the bottom of their foot. The area of dead skin will feel like you're standing on a rock.
The other reason people describe this sensation is because of a condition called Fat Pad Atrophy. This is when the natural cushioning on the bottom of the foot wears away. It essentially leaves you with no cushioning for the metatarsal bones. The "rocks" you feel are literally you walking on your bones.