My Orthopaedic Surgeon

Also known as Morton's metatarsalgia or Morton's neuroma, although Morton described neither (Morton thought this was a problem in the 4th MTP joint and Betts described the "neuroma" 70 years later).
The "neuroma" consists of degenerative and fibrotic changes in the common digital nerve near its bifurcation. However, there may be similar changes in adjacent unaffected nerves and it is not known why one becomes symptomatic. A number of causative factors have been suggested:
entrapment by the deep transverse metatarsal ligament
tethering of the 3rd space nerve by the anastomotic branch between medial and lateral plantar nerves
traction on the nerve by hindfoot valgus, interdigital bursitis or forced toe dosiflexion in high-heeled shoes

Interdigital neuritis is a mechanically induced nerve irritation due to intrinsic and extrinsic biomechanical factors that results in a combination of pain, paresthesias, or numbness in the forefoot. A greater understanding of forefoot anatomy and biomechanics has created an environment to further delineate the pathophysiology of interdigital neuroma.
Synonyms and related keywords: interdigital neuroma, interdigital neuritis, forefoot pain, forefoot paresthesias, forefoot numbness, foot pain, Morton's neuroma
Author: Thomas M Schaller, MD 2004

Morton neuroma (interdigital neuroma), first described in 1876, is a perineural fibrosis and nerve degeneration of the common digital nerve. Morton neuroma is not a true neuroma, although it results in neuropathic pain in the distribution of the interdigital nerve secondary to repetitive irritation of the nerve. The most frequent location is between the third and fourth metatarsals (third web space). Other less common locations are between the second and third metatarsals (second web space) and, rarely, between the first and second (first web space) or fourth and fifth (fourth web space) metatarsals. Episodes of pain are intermittent. Patients may experience 2 attacks in a week then none for a year. Recurrences are variable and tend to become more frequent. Between attacks, no symptoms or physical signs occur. Two neuromas rarely coexist on the same foot. Other diagnoses should be considered when 2 or more areas of tenderness are present.
Synonyms and related keywords: Morton's neuroma, Morton's metatarsalgia, interdigital neuroma, plantar neuroma, Morton metatarsalgia
Gonzalez & Bowman 2006

Wheeless' Textbook of Orthopaedics
Morton's Neuroma: Interdigital Perineural Fibrosis
it is not a neuroma but a perineural fibrosis and it was not first accurately described by Morton but by Durlacher, a chiropodist in 1845; both Thomas G. Morton (1876) and Thomas K. Morton (1892) mistook it for a painful affection of the fourth MTP articulation
- it is a type of nerve compression syndrome which involves the common digital nerves of the lesser toes: most often 3rd (80-85 %) and less often the 2nd (15-20 %) interspace;
- interdigital neuromas do not occur in the 1st and 4th web space: consider other etiologies;
- the occurance of two interdigital neuromas is also very rare;
- occurs most often in middle aged women (78 % are women);