Morton’s neuroma is caused by repeated pressure or irritation on a nerve in the ball of your foot, which triggers the tissue around the nerve to thicken and scar. It’s not actually a tumor despite the name. The condition is a buildup of fibrous tissue around one of the nerves running between your toes, most often between the third and fourth toes. It affects roughly 30 to 33% of the general population at some point, and women develop it four times more often than men.
What Happens Inside the Foot
Small nerves called common plantar digital nerves run between the long bones of your forefoot (the metatarsals) on their way to your toes. When one of these nerves gets compressed or irritated repeatedly, the body responds with inflammation and scarring. Over time, the tissue surrounding the nerve thickens with fibrous tissue, a process called perineural fibrosis. The nerve itself swells, loses some of its protective insulation, and the tiny blood vessel running alongside it can develop damage to its walls, sometimes even forming small clots.
This scarring and swelling is what creates the painful lump you can sometimes feel between your toes. It most commonly develops in the space between the third and fourth metatarsal bones, though the space between the second and third is the next most frequent location. The reason these spots are vulnerable comes down to anatomy: the nerves in these areas pass through a tight tunnel beneath a ligament that connects the metatarsal heads, leaving very little room for swelling before compression becomes painful.
How Footwear Contributes
Shoes are the single biggest modifiable cause. High heels shift your body weight forward onto the ball of the foot, increasing the load on the metatarsal heads. Narrow toe boxes squeeze those metatarsal heads together, pinching the nerve with every step. The combination of a raised heel and a tight front creates a kind of vice effect: the nerve is pushed up into a compressed space from below by the increased pressure, and squeezed from the sides by bones forced closer together.
This explains the large gender gap in prevalence. Women are far more likely to wear pointed, narrow, or high-heeled shoes over long periods. Switching to shoes with wider toe boxes and rocker-style soles reduces nerve pinching and limits the bending that occurs at the forefoot during walking. Flat, wide shoes won’t reverse existing fibrosis, but they can slow its progression and significantly reduce pain.
Sports and Repetitive Impact
Any activity that puts repeated pressure on the ball of the foot can irritate the interdigital nerve enough to start the scarring process. Running and jogging are common culprits because each stride drives force through the forefoot hundreds or thousands of times per session. Racquet sports like tennis involve quick lateral movements that shift weight onto the metatarsal heads. Rock climbing and skiing are notable because the shoes involved are intentionally tight and stiff, compressing the forefoot for extended periods.
The mechanism is cumulative. A single long run won’t cause Morton’s neuroma, but months or years of repetitive forefoot loading, especially in poorly fitting athletic shoes, can gradually damage the nerve and trigger the fibrous response. Athletes who increase training volume quickly or switch to shoes with less forefoot room are at higher risk during that transition.
Foot Structure and Biomechanics
The shape of your foot plays a role in how much stress reaches the interdigital nerves. People with high arches tend to carry more weight on the ball of the foot because the arch doesn’t absorb as much shock during walking. Those who overpronate (feet that roll inward excessively) can also place uneven pressure on the metatarsal area. Bunions, hammertoes, and other deformities that alter the alignment of the forefoot change where force concentrates during each step, sometimes funneling extra pressure into the spaces where these nerves sit.
These structural factors don’t guarantee you’ll develop a neuroma, but they lower the threshold. Someone with high arches wearing narrow shoes and running regularly is stacking multiple risk factors. Addressing any one of those factors, through orthotics, shoe changes, or activity modification, can reduce the total load on the nerve.
Who Gets It Most Often
The typical patient is a middle-aged woman. In clinical studies, the average age at diagnosis is around 45 to 46 years, though it can develop in anyone from their late teens through their sixties. The 4-to-1 female-to-male ratio is partly explained by footwear patterns, but hormonal and anatomical differences in foot structure may also contribute. Women tend to have slightly wider forefeet relative to the shoes available to them, and ligament laxity differences may change how the metatarsal heads move under load.
How It’s Identified
Diagnosis usually starts with a physical exam. The most accurate hands-on test involves the examiner squeezing the affected area between thumb and index finger, which has about 96% sensitivity in detecting a neuroma confirmed by ultrasound. A more well-known test called Mulder’s click, where the examiner squeezes the forefoot side to side while pressing up on the affected space, produces an audible or palpable click as the swollen nerve pops between the metatarsal heads. This test is less reliable at around 61% sensitivity, and it tends to be positive only when the neuroma is larger, averaging about 11 mm compared to 8.5 mm in cases where the click is absent.
If the physical exam is inconclusive, ultrasound or MRI can confirm the diagnosis and measure the size of the fibrous mass. Size matters for treatment planning: smaller neuromas often respond to conservative measures like shoe modifications and padding, while larger ones may need more intervention.
Why It Gets Worse Over Time
Morton’s neuroma is a progressive condition when the underlying cause isn’t addressed. The cycle works like this: compression irritates the nerve, irritation causes swelling, swelling makes the nerve take up more space in an already tight tunnel, and the increased size leads to more compression. Each round of inflammation adds more fibrous tissue, and unlike muscle or skin, this scar tissue doesn’t remodel well on its own. The nerve gradually loses more of its myelin insulation, making it increasingly sensitive to pressure that wouldn’t have bothered it earlier.
This is why early intervention matters. The same nerve compression that causes occasional tingling after a long walk in heels can, over months or years, become a constant burning pain that makes even flat shoes uncomfortable. Reducing the mechanical causes early, before significant fibrosis develops, gives the nerve the best chance of recovering without surgical intervention.