Morton’s Neuroma

A burning pain in the ball of the foot that spreads into two toes, the sense of a pebble in your shoe, relief when you take the shoe off and rub the foot — that pattern is a Morton’s neuroma. It is a thickening of one of the small nerves that run between the long bones of the foot, and it is one of the commonest causes of pain in the forefoot. Most people are managed with changes to footwear and, where needed, an injection. Surgery is reliable for those who need it, but it comes with a permanent patch of numbness that you should know about beforehand.

What a Morton’s neuroma is

The nerves that supply feeling to the toes pass between the heads of the metatarsal bones, beneath a tight ligament that joins them. Where a nerve is squeezed there, over and over, its sheath thickens and scars. Despite the name it is not a tumour and it does not spread; "neuroma" simply describes the swollen nerve. It most often affects the nerve between the third and fourth toes, next most often the one between the second and third, and it is far more common in women — narrow shoes and heels push the metatarsal heads together and load the front of the foot.

Symptoms

• burning, sharp or electric pain under the ball of the foot, radiating into the two toes either side of the affected nerve

• tingling or numbness in those toes

• the feeling of standing on a pebble, or of a sock bunched up under the foot

• pain that is worse in enclosed or heeled shoes and with walking, and eases when the shoe comes off and the foot is rubbed

• symptoms that come and go over months, gradually becoming more frequent

Why it happens

Anything that compresses the front of the foot: tight or pointed shoes, high heels, a lot of time on the balls of the feet in running or court sports, and foot shapes that crowd the metatarsals together — a bunion, hammer toes, or a long second metatarsal. Sometimes there is no clear reason.

Other causes of pain in the ball of the foot

Several conditions mimic a neuroma and are treated differently, so the diagnosis matters. A tear of the plantar plate — the ligament under the second toe joint — causes pain under the joint itself, often with the toe starting to lift or drift, and is frequently mislabelled as a neuroma. Inflammation of the joint lining, a stress fracture of a metatarsal, a bursa between the metatarsal heads, and thinning of the fat pad under the forefoot all cause pain in the same area. Part of the consultation is telling these apart.

How it is assessed

The examination usually makes the diagnosis: tenderness in the web space between the toes rather than under the joint, and a characteristic click when the forefoot is squeezed from side to side and the neuroma slips between the bones. An ultrasound confirms it, measures it and, importantly, checks for a plantar plate tear or a second neuroma; it is also used to guide injections. An MRI is used when the ultrasound is unclear or another problem is suspected. Weightbearing X-rays exclude a stress fracture or arthritis.

Non-surgical treatment

This is where treatment starts, and it settles many people.

• Footwear — a wide, deep toe box and a low heel, which takes the squeeze off the nerve. This is the single most effective change, and it is worth being honest with yourself about your shoes.

• A metatarsal dome — a small pad placed just behind the ball of the foot, which spreads the metatarsals and lifts pressure off the nerve. Cheap, and often very effective.

• Orthotics — an insole with a built-in dome and arch support where foot shape is contributing.

• Activity changes — less time on the balls of the feet while it settles.

• A corticosteroid injection — done under ultrasound guidance around the nerve. It reduces the swelling and gives relief that lasts months in many people, and for some it is enough. It is limited to one or two, because repeated steroid thins the fat pad under the foot and can discolour the skin.

Surgery

Where footwear and an injection have not controlled the pain, the neuroma is removed. Through a short incision on the top of the foot between the two toes, the ligament over the nerve is released and the thickened segment of nerve is cut out, with the nerve divided well back so that the cut end sits away from the weightbearing surface. It is done as day surgery, usually under a general anaesthetic with local anaesthetic for the first hours afterwards.

Because a section of nerve is removed, the skin between the two toes is permanently numb afterwards. Most people find this a fair trade for losing the pain, but it is permanent, and it is the thing to be clear about before deciding.

Recovery

You walk on the foot from the first day in a firm post-operative shoe, keeping it elevated as much as possible for the first week. The wound is checked at two weeks, after which you move back into a wide, comfortable shoe. Most people are driving at two to three weeks and back to normal activities by four to six weeks; running and narrow shoes wait until the forefoot is comfortable, usually a couple of months. Some swelling in the front of the foot lasts for several months.

Risks

Every operation carries risk. The specific ones here are the expected numbness between the toes; a tender scar; wound problems and infection; blood clots; a painful regrowth at the cut end of the nerve — a stump neuroma — which can need a second operation; and pain that persists because the neuroma was not the only cause.

Dr Janan's approach

Dr Janan Chandrananth is a foot and ankle orthopaedic surgeon who completed fellowship training in Bristol and in Tokyo, the latter under a past president of the Japanese Society for Surgery of the Foot. Forefoot pain is one of the commonest problems he sees.

His approach is to be sure the pain is coming from the nerve — a plantar plate tear or a stress fracture treated as a neuroma helps no one — and to use footwear and a guided injection before an operation is discussed. Where surgery is needed it is a short day procedure with a quick recovery, and the numbness that follows is explained plainly beforehand.