The Science of Morton's Neuroma

Morton's neuroma, more accurately termed intermetatarsal neuroma, represents a localized thickening of the common digital nerve as it passes beneath the deep transverse metatarsal ligament. Despite its name, this condition is not a true neuroma but rather perineural fibrosis - a reactive thickening of the nerve sheath and surrounding connective tissue. The condition most commonly affects the third intermetatarsal space (between the third and fourth metatarsals) due to unique anatomical factors. In this location, the medial and lateral plantar nerves converge, creating a larger nerve bundle that is more susceptible to compression. The nerve becomes trapped between the metatarsal heads above, the deep transverse metatarsal ligament below, and compressed laterally by adjacent metatarsals during toe-off. Repetitive mechanical irritation leads to chronic inflammation of the nerve sheath, followed by progressive fibrosis and thickening. This creates a pathological cycle where the enlarged nerve becomes increasingly susceptible to further compression. The resultant ischemia and mechanical deformation of nerve fibers produces the characteristic neuropathic pain symptoms. Contributing factors include biomechanical abnormalities that increase forefoot loading, such as excessive pronation, first ray insufficiency, or metatarsal length variants. Intrinsic factors like hammertoe deformities or claw toes can further compress the intermetatarsal spaces. The condition is significantly more common in women (8-10:1 ratio), largely attributed to restrictive footwear with narrow toe boxes and elevated heels that force the metatarsals together and increase forefoot loading.