What Causes Neuromas?

There are many factors that may cause or aggravate a neuroma. First, there are several foot structural pathologies that may contribute to neuroma pain. An abnormally pronated foot structure (flat foot) can be attributed to neuroma formation. A flat foot structure leaves the forefoot unstable when pushing off the ground while stepping forward. This instability causes increased rubbing forces that can irritate the plantar nerves involved in neuroma formation. It is also important to note that during propulsion, while the toes flex, the nerve is pulled taut against the deep transverse intermetatarsal ligament. This may irritate and worsen neuroma symptoms. Earlier theories suggest that compressive forces between the third and fourth metatarsal heads may result in the chronic traumatic changes that occur within the nerve.

Certain types of shoes may also contribute to nerve irritation. In particular, many women's shoes leave a foot susceptible to neuroma pain. High-heeled shoes keep toes in a flexed position, pulling the plantar nerves taut against the overlying deep transverse intermetatarsal ligament. In addition, weight forces through the foot are more vertical; this greatly increases the pressure applied to these nerves. Narrow and/or pointed shoes may also result in compression of the metatarsal heads, trapping the plantar nerve. All of these factors lead to nerve irritation, inflammation and subsequent neuroma formation.

Other factors that may cause or worsen a neuroma include inflammatory conditions such as arthritis. Also, activities that involve repetitive trauma to plantar nerves may contribute to neuroma formation. For example, repetitive pounding on a hard surface in sports like racquetball and jogging results in shearing and irritation of the nerve. Cysts, soft tissue masses, or tumors may compress the nerve and cause neuroma-like symptoms. Lastly, direct acute trauma may result in neuroma formation.