Morton’s neuroma is also known as Morton’s metatarsalgia, Morton’s neuralgia, plantar neuroma and inter metatarsal neuroma. While the exact cause of Morton’s neuroma is still not known, compression (i.e. entrapment) of the common plantar digital nerve is generally accepted as the reason for the condition.
The common plantar digital nerve provides sensation to the webspace between the third and fourth toes and runs very close to an important supporting ligament of the forefoot, called the transverse intermetatarsal ligament which runs across the forefoot bones. Due to injury, overflexion of the foot, or narrow tight shoes, this ligament rubs against the nerve and irritates it resulting in a perineural neuroma.
The continual pressure on the nerve causes the irritation reaction to reoccur becoming chronic resulting in fibrosis within the nerve and thickening of the nerve. Unfortunately, this thickened, fibrotic nerve further compresses the nerve cells causing greater pain. The pain can become so intense that it prevents weight bearing and walking.
Morton’s neuroma is a common condition of the foot that affects women more often than men, with a female-to-male ratio of 4:1. They tend to occur in ages 50 – 60 although Morton’s neuroma can occur at any age in which a great deal of walking or exercising occurs.
Certain risk factors make Morton’s neuroma more likely. For instance, wearing narrow or high-heeled shoes is a well-known cause of this condition, and an important part of treatment focuses on wearing shoes that allow more space for the foot and toes.
High impact activities, such as running or jogging, can put pressure on the ligament and cause thickening of the nerve. Sports are another common cause of Morton’s neuroma. Certain sports that require tight fitting shoes, such as skiing, are more likely to cause Morton’s neuroma.
Finally, deformities of the feet, such as hammer toes, bunions, and flat feet, can cause the ligament to press on the nerve. In some cases, wearing supportive shoes can help when this is the cause of the condition, but more aggressive treatments may be necessary to correct the foot deformity.
For an in-depth discussion of Morton’s neuroma see A Scientific Discussion of Morton’s neuroma.