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On Your Feet! Morton's Neuroma
pathology perspectives

By Ruth Werner

Originally published in Massage Bodywork magazine, May/June 2009. Copyright 2009. Associated Bodywork and Massage Professionals. All rights reserved.

This issue of Massage Bodywork is dedicated to practitioner safety. From a pathology perspective, practitioner safety creates an opening for a number of different discussions. Our profession has several occupational hazards, and we invest significant time and energy during our education to minimize these risks. We learn important hygienic practices for our clients' protection, but also to keep ourselves safe from the threat of infectious diseases spread through skin-to-skin contact. We learn good body mechanics to preserve the life expectancy of our hands and our backs. But one under-addressed group of hazards is common to massage therapists and anyone else who spends much of their work day standing: foot problems.

In the realm of bodywork practitioner safety, foot pain may seem like a minor issue, but it can certainly degrade the quality of life for the person who has it. At the risk of overstating the obvious, feet comprise the surface area through which we respond and adapt to gravity. As we well know, any misalignment or imbalance of forces in the feet can have system-wide implications: one foot hitting the ground wrong can torque a knee, twist a hip, subluxate a sacroiliac joint, and eventually cause headaches as those directional forces reverberate. More locally, if a foot malfunctions because of some internal misalignment, compensation patterns can increase the risk for other foot problems. In this way, a bunion can lead to ligament instability; plantar fasciitis can contribute to metatarsal pain; jammed arches can contribute to hammertoe; and any dysfunction can contribute to the development of this article's topic, Morton's neuroma.

Imagine the sensation of having a marble lodged in the ball of your foot, or a bolt of electrical pain that shoots into your toes with every step: that is the sensation of Morton's neuroma.


Anatomy Review

To understand this problem well, and to strategize how to prevent it or use massage to address it, we need to take a brief look at some relevant aspects of foot anatomy. The metatarsals make up the long part of the foot and are numbered 1-5 from the medial to the lateral side. The range of motion at the tarsal-metatarsal joints is very limited: the bones can move just enough to allow the arches of the foot to flatten and rebound with each step. However, mobility of these joints increases toward the lateral aspect: the 4th and 5th metatarsals move more freely than their medial partners.

Nerve supply for the distal part of the foot is provided by the common digital nerves. These nerves are the terminal endings of the lateral and medial plantar digital nerves, which originate as part of the sciatic nerve. This is significant, because any restriction or limitation of free movement from the buttocks downward can irritate nerve fibers that eventually reach the bottom of the foot. The common digital nerves converge at the metatarsal heads, or "balls" of the feet. This location is especially vulnerable to compressive forces: the nerve structures are thick where they converge and their location is superficial to both the metatarsal heads and the transverse intermetatarsal ligaments. In other words, this bulkiest part of the nerve with its connective tissue sheath is in a position to be squeezed and irritated from all sides when pressure is translated across the bottom of the foot and toward the toes, as during the "toe-off" phase of walking.


Contributing Factors To Morton's Neuroma

When branches of the common digital nerves converge and are irritated by compressive forces, the structure's connective tissue sheath tends to thicken. This protective response adds to compression on the nerve and exacerbates symptoms of nerve irritation. Morton's neuroma turns out not to be a true neuroma (nerve tumor) at all. A more correct term is perineural fibrosis: a thickened perineurium, or nerve sheath.

Tight Fascia and Muscles

Several issues can contribute to nerve irritation in the ball of the foot. For example, the nerve might be embedded in thick fascia all the way down the leg. If that fascia is tight and restrictive, it inhibits the ability of the nerve to function well and increases the risk of entrapment or stretching of the nerve. Additionally, muscle tightness in the hamstrings or plantar flexors can pull on or compress the medial and lateral plantar nerves that eventually become the common digital nerves. People who spend a lot of their day in high heels put particular pressure at the metatarsal heads, just where the nerves are compressed under the intermetatarsal ligaments. This is exacerbated by squatting with the feet in plantar flexion: this is a position often adopted by people with tight hamstrings and calf muscles when they must squat.

Other Foot Problems

Compensation patterns in the feet can also contribute to compression of the common digital nerves. Plantar fasciitis is a condition involving damage to the plantar fascia of the foot, making it painful to walk through a normal range of foot motion. For these people, spreading the arches of the foot is irritating, so they tend to walk on the balls of their feet and thus pressure on the common digital nerves under the metatarsal heads. Pes planus (flat feet) or pes cavus (jammed arches) likewise create compensation patterns that alter how force is transferred through the bottom of the feet. With little or no rebounding action in the arches of the feet, the nerves have no protection from constant compression. Any condition that alters how weight is distributed through the foot can contribute, including plantar warts, bunions, and even temporary blisters.

Footwear

It won't come as a surprise that high-heeled shoes are a major contributor to the biomechanical forces that lead to Morton's neuroma. Wearers of high heels with a narrow toe box are especially prone to this disorder. This probably explains why women are affected nearly five times more frequently than men. But even flat shoes can create a problem if they offer inadequate protection of the metatarsal heads. Worn-down shoes with flattened padding can be as potent a contributor to perineal fibrosis as spike heels.


Symptoms, Diagnosis

The signs and symptoms of Morton's neuroma are easy to predict, because nerve irritation creates a characteristic shooting, electrical sensation that travels distally. Consequently, if the nerves between the metatarsals are sufficiently irritated, they send a jolt of pain distally to the toes. Long-term irritation may lead to tingling or numbness in the same location. This almost always happens between the 3rd and 4th metatarsals, but it can also happen at the space between the 2nd and 3rd metatarsal. It almost never happens outside this range: pain from far medial or lateral metatarsals must be investigated as something other than Morton's neuroma.

A clinical exam for this condition may aim to recreate the pain associated with this condition. Many clinicians also look for a characteristic sound ("Mulder's click") when the metatarsals are compressed. Mulder's click can occur without nerve irritation, however, so it is not in itself a definitive diagnostic marker. If a clinical exam is inconclusive, an MRI or ultrasound might be recommended, but these tests are often unnecessary.

Unfortunately, a host of other foot problems can both mimic and occur simultaneously with Morton's neuroma. In order to create the best possible treatment strategy, these conditions must be either ruled out or identified, along with thickening of the perineurium. A short list of the possibilities for differential diagnosis includes:

Tarsal Tunnel Syndrome

This is compression or irritation of the tibial nerve as it passes on the medial ankle under the retinaculum ligament. This can occasionally refer pain specifically to the toes.

Stress Fractures

Tiny hairline fractures of the metatarsals, sometimes called march fractures, can create pain in the distal foot. These can be difficult to see on an X-ray and may need more intrusive testing to definitively identify.

Metatarsalgia

This is a general name for pain at the ball of the foot. It is often traced to overuse and worn-down footwear. It usually affects more of the foot than Morton's neuroma, and the pain tends to be achy and superficial rather than deep and electric.

Osteoarthritis, Rheumatoid Arthritis

These conditions involve joint inflammation, but no specific nerve irritation.

Hammertoe

In this situation, an imbalance in the muscles of the toes creates permanent flexion at the interphalangeal joints. It is most common in the same toes affected by Morton's neuroma and may occur simultaneously with it.

Ganglion Cyst

Usually seen on the hands, ganglion cysts are pouches that grow on tenosynovial sheaths. If such a growth occurs on the tenosynovial sheaths of the toes, it could create symptoms very similar to Morton's neuroma, but the treatment strategy would have to be different.


Treatment Options

Morton's neuroma is treatable, but as with so many things, treatment tends to be most successful if it is initiated early in the process. Noninvasive strategies are often successful. These can include changing footwear to flat, well-supported shoes, or using specially designed orthotics or pads to cushion the metatarsal heads. Careful stretching of the foot, calf, and hamstrings can also help, as the nerve fibers can be caught anywhere along their distance. Finally, many people get good relief with massage: even an informal foot rub can temporarily resolve symptoms.

If noninvasive interventions aren't successful, however, then Morton's neuroma patients may have to explore other options. Corticosteroids may be injected into the area of the fibrosis to try to dissolve excessive connective tissue. If nerve pain is intractable, the nerve may be permanently deadened with an alcohol injection. The thickened structure may also be surgically removed, but of course the consequences for this type of foot surgery include permanent numbness, muscle atrophy, and risk of infection.


Massage for Morton's Neuroma

This is one condition where a careful massage strategy can yield important and lasting results. Several tactics can be considered in using manual therapies for Morton's neuroma.

Go Where It Is

In other words, as long as sensation is present and nothing aggravates the pain, massage directly in the areas affected by Morton's neuroma can offer great relief. Work that emphasizes making space between the metatarsal heads will probably be the most effective.

Go Where It Isn't

Massage and stretching to the entire posterior aspect of the leg can have a profound affect on the functioning of the nerves that terminate in the toes. From the gluteals and deep lateral rotators to the hamstrings and all the plantar flexors (gastrocnemius, soleus, tibialis posterior, and the deep toe flexors), massage can reduce muscle tension and release fascial restrictions--both of which can allow the affected nerve tissue to move and work more freely.
The prognosis for a person with Morton's neuroma is usually excellent--especially if massage is used as part of a treatment strategy--and it is refreshing to be able to discuss a condition where massage can have such an obvious and directly observable benefit.

It is important to remember that this article was written in the context of our own occupational hazards. Massage therapists and bodywork practitioners who are on their feet for many hours a day are well-advised to take extra care with the quality of their footwear and to invest in what we all know is more than a self-indulgent treat. In case you haven't had one lately, let this article be a catalyst: go get a massage!

Ruth Werner is a writer and educator who teaches several courses at the Myotherapy College of Utah and is approved by the NCBTMB as a provider of continuing education. She wrote A Massage Therapist's Guide to Pathology (Lippincott Williams Wilkins, 2009), now in its fourth edition, which is used in massage schools worldwide. Werner is available at www.ruthwerner.com or wernerworkshops@ruthwerner.com.




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