A neuroma is a thickening of nerve tissue that may develop in various parts of the body. The most common neuroma in the foot is a Morton's neuroma, which occurs at the base of the third and fourth toes. It is sometimes referred to as an intermetatarsal neuroma. "Intermetatarsal" describes its location - in the ball of the foot between the metatarsal bones (the bones extending from the toes to the midfoot). Neuromas may also occur in other locations in the foot.
The thickening, or enlargement, of the nerve that defines a neuroma is the result of compression and irritation of the nerve. This compression creates swelling of the nerve, eventually leading to permanent nerve damage.