Orthopedics & Podiatry & Family Medicine
Morton's neuroma
Morton's neuroma — also known as Morton's neuralgia, interdigital neuroma, or plantar neuroma—is a painful condition of the forefoot resulting from perineural fibrosis and degeneration of the connective tissue surrounding a common plantar digital nerve compressed between the metatarsal heads. Despite its name «neuroma,» it is not a true nerve tumor but a reactive fibrotic response to chronic mechanical irritation of the nerve—hence some authors’ preference for the terms perineuromatous fibroma or interdigital neuralgia. The interdigital space between the 3rd and 4th toes is affected in 65 to 70% of cases, while the space between the 2nd and 3rd toes is affected in 20 to 30% of cases — the predilection for these spaces is explained by the anastomosis of the branches of the medial plantar nerve and the lateral plantar nerve in these spaces, creating a larger-caliber nerve that is particularly sensitive to compression by the transverse metatarsal ligament during weight-bearing. Morton’s neuroma predominantly affects women (ratio 4 to 8 to 1), likely due to the more frequent use of narrow-toed and high-heeled shoes that compress the forefoot and increase pressure on the intermetatarsal spaces. The diagnosis is clinical, supported by musculoskeletal ultrasound (the first-line imaging method) or foot MRI in doubtful cases. Management begins with conservative measures (shoe modifications + orthotic insoles + ultrasound-guided corticosteroid injections) with a long-term success rate of 50 to 70%, and continues with surgical neurectomy (removal of the neuroma) for refractory cases, offering a complete relief rate of 85 to 90%.
Pathophysiology and anatomy
- Anatomy of the intermetatarsal space: the common plantar digital nerves run in the intermetatarsal spaces under the deep transverse intermetatarsal ligament that connects the metatarsal heads together + when standing and walking → the metatarsal heads come closer together → the transverse intermetatarsal ligament compresses the digital nerve between the metatarsal heads and the sole of the foot + repeated compression during weight-bearing → repeated microtrauma to the nerve
- Preference for the 3rd interdigital space in the 3rd space, the common digital nerve results from the anastomosis of the lateral branch of the medial plantar nerve and the medial branch of the lateral plantar nerve → nerve more voluminous than elsewhere → more sensitive to compression in an anatomically narrower space + the 2nd space is the second most frequently affected by the same mechanism
- Histological lesions: progressive epineural and perineural fibrosis → thickening of the nerve sheath → axonal degeneration → hyaline deposits around the perineural vessels → endoneural edema → macroscopic appearance of a firm, whitish 5-10 mm fusiform mass surrounding the digital nerve + this is not tumor cell proliferation but reactional fibrosis
- Aggravating factors : narrow-toe shoes compress the forefoot transversely + high heels increase the load on the anterior metatarsals (the metatarsal heads support up to 75 % of body weight with a 5 cm heel) + repeated-impact sports activities (running + tennis + dance) + flat or hollow foot with unbalanced metatarsal pressure distribution + associated intermetatarsal bursitis (often concomitant with neuroma)
Clinical presentation
| Sign or symptom | Detailed clinical description | Diagnostic value |
|---|---|---|
| Burning or electric metatarsalgia | Burning, throbbing, and electric shock-like pain in the forefoot, radiating to the two toes adjacent to the affected area (e.g., 3rd and 4th toes for the 3rd interspace), or toward the sole of the foot. Worsened by walking on hard surfaces, prolonged standing, running, and wearing narrow or high-heeled shoes. Relieved by rest, removing shoes, and massaging the forefoot. | Pain radiating to both pinch toes (not to a single dermatome) is characteristic of Morton's neuroma + immediate relief upon removing shoes is a very suggestive clinical sign |
| Tingling and numbness of the toes | Tingling + numbness + feeling of a scarf between the toes + or having a pebble in the shoe + affecting the two toes on either side of the affected space + sometimes permanent in advanced forms | Bilateral paresthesias in the two toes adjacent to the painful area—a neurological sign pointing to the intermetatarsal digital nerve. |
| Mulder's sign | Forefoot lateral compression (squeeze test) — simultaneous pressure on both sides of the foot over the metatarsal heads with one hand + direct compression of the painful interdigital space with the thumb of the other hand → reproduction of characteristic pain + sometimes perception of a Mulder's click (palpable clicking sensation as the neuroma moves between the metatarsals) | Positive Mulder's sign → sensitivity 40–84% (%) + specificity 95–100% (%) → the most specific clinical sign in the entire clinical picture of Morton's neuroma |
| Interdigital hypoesthesia | Reduced sensitivity to light touch or pinprick in the corresponding interdigital space or between two adjacent toes may be accompanied by decreased two-point discrimination. | Present in 50–60% of confirmed cases + indicates chronic axonal compression of the digital nerve + has confirmatory diagnostic value |
| Associated intermetatarsal bursitis | Inflammation of the intermetatarsal bursae, often occurring concurrently with neuroma, accompanied by swelling and tenderness upon direct palpation of the dorsal intermetatarsal space, contributing to pain and local nerve compression. | Frequently associated with neuromas (50–75% of cases) + visible on ultrasound as hypoechoic collections + isolated bursitis without a neuroma can mimic the clinical presentation |
ℹ️
The main differential diagnoses for Morton's neuroma in clinical practice are mechanical metatarsalgia due to stress (overload of the 2nd or 3rd metatarsals, common after surgery for hallux valgus), metatarsal stress fracture (pain upon direct palpation of the metatarsal shaft, not the interdigital space), and metatarsophalangeal synovitis or bursitis. A careful clinical examination—particularly the location of pain on palpation (interdigital space = neuroma; metatarsal head or shaft = mechanical metatarsalgia) and the presence of Mulder's sign—most often allows for differentiation before ultrasound.
Diagnostics and imaging
- Musculoskeletal ultrasound — first-line examination: high-frequency probe (15 to 18 MHz) + visualization of the interdigital space in longitudinal and transverse section + the neuroma appears as a well-defined hypoechoic mass (fusiform or oval) in the plantar interdigital space beneath the intermetatarsal ligament + typical size 5 to 10 mm (a neuroma smaller than 5 mm is rarely symptomatic) + Mulder's sign can be reproduced dynamically under real-time ultrasound + can also be used to visualize associated bursitis (adjacent anechogenic collection) + guides therapeutic infiltrations + sensitivity 90 % + specificity 85 % for symptomatic neuromas
- MRI of the foot: indicated if ultrasound is inconclusive or if diagnosis is difficult + mass in plantar interdigital space with T1 hypointensity and T2 iso-hypointensity + perineural enhancement after gadolinium + more sensitive than ultrasound for small neuromas (< 5 mm) + useful for visualizing associated bursitis + higher cost and less availability than ultrasound → second-line examination
- Standard foot X-ray: systematically performed as first-line treatment for any metatarsalgia + normal in Morton's neuroma (no visible bone lesion) + helps rule out fatigue fracture + metatarsophalangeal osteoarthritis + hallux valgus + bone deformities + metatarsal osteophytes
- Anesthetic diagnostic block injection of local anesthetic (lidocaine 2 %) into the suspected interdigital space + complete and immediate disappearance of pain confirms diagnosis and predicts response to therapeutic corticosteroid infiltration + simple and inexpensive technique + used to confirm diagnosis before surgical decision
Processing — Step-by-step strategy
| Treatment | Terms and Protocol | Success Rate and Remarks |
|---|---|---|
| Shoe modification – mandatory first step | Shoes with a wide toe box (at least as wide as the widest part of the foot) + low heel (less than 3 cm) + flexible sole + permanent discontinuation of pointed-toe and high-heeled shoes + this change alone improves symptoms in 30 to 50% of mild cases if adopted early in the course of the condition | Fundamental + essential + often insufficient on its own in moderate to severe cases + to be systematically associated with all other treatment steps |
| Orthotics and shoe inserts | Insole with metatarsal bar (metatarsal pad placed behind the metatarsal heads) → redistributes load to the metatarsal shafts by unloading the heads + depression insole in the painful interdigital space → reduces direct nerve compression + custom-made or semi-custom-made + to be worn continuously in all shoes worn | Symptom reduction of 30–50% in observational studies + should be combined with changes in footwear + better results if the neuroma is small and recent + less effective for older, fibrous neuromas |
| Ultrasound-guided corticosteroid injection | Injection of a long-acting corticosteroid (methylprednisolone 40 mg + triamcinolone 40 mg) + local anesthetic (lidocaine 1:1:3) into the interdigital space + dorsal or plantar approach + ultrasound guidance strongly recommended for accuracy and effectiveness + 1 to 3 injections spaced 4 to 6 weeks apart + to be combined with orthopedic measures | Short-term relief (3 to 6 months) in 50 to 70% of patients + frequent relapses after 6 to 12 months + ultrasound guidance increases the success rate compared to blind injection + no more than 3 injections per year (risk of plantar fat pad atrophy + superficial skin necrosis + rupture of the intermetatarsal ligament) |
| Absolute alcohol sclerotherapy injections | Perineural injections of absolute alcohol at 4–10 cm (series of 4 to 6 weekly injections) guided by ultrasound + mechanism: fibrillation and sclerosis of nerve fibers → reduction in neuroma size and pain | Success rates of 60–80% in published series + comparable to surgery in some studies + technique rarely used in North America but more widely adopted in Europe + lack of high-quality randomized trials + alternative to surgery for patients who are contraindicated forgeneral anesthesia |
| Surgical neurectomy (neuroma excision) | Excision of the neuroma and corresponding segment of digital nerve under general or regional anesthesia + dorsal approach (more common — incision between the metatarsals + section of the transverse intermetatarsal ligament + resection of the neuroma) or plantar approach (direct access + plantar scar but risk of keloid) + outpatient in most cases + resumption of walking in wide shoes on day 1 + complete return to activity in 4 to 6 weeks | Rate of complete or very significant relief: 85–90% in the long term + nerve resection results in permanent hypoesthesia of the corresponding nerve distribution (often well tolerated and preferable to pain) + regrowth neuroma on the stump (recurrent neuroma) in 5 to 10% of cases → requires reoperation + indicated after failure of 3 to 6 months of properly conducted conservative treatment |
Medical consultation recommended
A medical consultation is recommended for any forefoot pain that persists for more than 4 to 6 weeks despite wearing appropriate footwear, especially if the pain radiates to two adjacent toes, is aggravated by walking, and is relieved by rest and removing shoes. A diagnosis of Morton's neuroma justifies a clinical evaluation and an ultrasound of the forefoot to confirm the diagnosis and rule out a metatarsal stress fracture or other bone pathology before initiating treatment.
For the evaluation of metatarsalgia, the prescription of an ultrasound of the forefoot and an X-ray, the administration of an ultrasound-guided corticosteroid injection, or referral to an orthopedic surgeon or podiatrist for resistant cases, Clinique Omicron offers medical consultations at its service points in Quebec and via telemedicine. To book an appointment, visit cliniqueomicron.ca.
Consult at Clinique Omicron
Clinique Omicron's physicians and nurse practitioners (NPs) evaluate patients with metatarsalgia or forefoot pain suspected to be Morton's neuroma, order foot X-rays and musculoskeletal ultrasounds, initiate appropriate orthopedic advice (footwear + orthotics), perform or refer for ultrasound-guided corticosteroid injections, and refer to an orthopedic surgeon or podiatrist for cases refractory to conservative treatment. Consultations are available at several service points in Quebec and via telemedicine. To make an appointment, visit cliniqueomicron.ca.
The content of this page is for informational purposes only and is not a substitute for the advice of a doctor, podiatrist, or orthopedic surgeon. The diagnosis of Morton's neuroma requires appropriate clinical evaluation and imaging to rule out other forefoot pathologies before initiating treatment.
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