What is Morton’s Neuroma?
Morton’s Neuroma is a common and painful condition of the ball of the foot. It comes about when the small nerve running between the long bones of the forefoot (metatarsals) is squeezed, just before its entry into two of the toes. This is usually the third and fourth, sometimes also the second and third toes and rarely between the fourth and fifth toes.
In the diagram, you can see that the nerve divides into two parts between the metatarsal heads, at the point where the space between the bones is narrower. If the nerve is repeatedly damaged by being compressed between the bones, the nerve will thicken, forming a mass on the nerve at this point. The larger the nerve becomes, the greater the likelihood of it being trapped between the bones and so the problem can get progressively worse.
What are the symptoms of Morton’s Neuroma?
Morton’s Neuroma pain occurs almost exclusively when wearing shoes. This is because there is less space between the metatarsal bones the tighter the shoes are. People generally use words like electric shock, burning and searing pain to describe their experience. The pain is felt in the ball of the foot but also extending into two toes. There may also be a clicking sensation that occurs at the time of the compression, known as a “Mulder’s click”. This happens as the swollen nerve is squeezed so hard between the bones that it ‘pops out’ either the top or the bottom, depending on whether it is the dorsal or plantar nerve that is entrapped.
What causes a Morton’s Neuroma?
Morton’s Neuroma comes about when there is not enough room for the nerve in the inter metatarsal space. Poorly fitting shoes can squeeze this space in obvious ways. Less well known is that rolled in, or pronated, feet can also be implicated in the problem. Pronation makes a difference because the metatarsal bones are deeper than they are wide. When the foot is in a good position, the bones are at their thinnest. When the foot slumps in, the bones rotate about their long axis and take up more room side to side.
How do you treat Morton’s Neuroma?
The treatment ladder is as follows:
Footwear: For some people, changing shoes may be all that is required.
Making more space between the metatarsal bones: Padding can be used to spread the toes apart or to lift up one metatarsal of the colliding pair. If this is not sufficient, orthotics can be used to straighten the whole foot and therefore rotate the metatarsal bones to their thinnest position.
Injections: Glucose injections can calm the nerve and reduce its size. These are done simply in the podiatrists chair and are well tolerated. They can be done from the top surface of the foot which is less painful than from underneath. Corticosteroids can also be done in the clinic, though generally these are done from below after using a local anaesthetic. Corticosteroids generally could be expected to have a more rapid reduction in pain than glucose.
Nerve treatment: If the fibre of the nerve is painful to touch across the top of the foot, over the ankle or up the leg, further investigation is necessary. It is possible that there is a nerve entrapment higher up on the nerve, manifesting symptoms into the forefoot.
Surgery: Rarely used as the simple treatments are very effective for this condition.