Orthopedics & Podiatry & Family Medicine
Morton's neuroma
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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», this is not a true nerve tumour, but a fibrotic reaction to chronic mechanical irritation of the nerve - hence the preference of some authors for the term perineuromatous fibroma or interdigital neuralgia. The interdigital space between the 3rd and 4th toes is affected in 65 to 70 % of cases, the space between the 2nd and 3rd toes in 20 to 30 % of cases - the predilection for these spaces is explained by the anastomosis of branches of the medial plantar nerve and lateral plantar nerve in these spaces, creating a larger-calibre nerve particularly sensitive to compression by the transverse intermetatarsal ligament during weight-bearing. Morton's neuroma is more prevalent in women (ratio 4 to 8:1), probably due to the more frequent use of narrow-toed, high-heeled shoes, which compress the forefoot and increase pressure on the intermetatarsal spaces. Diagnosis is clinical, backed up by musculoskeletal ultrasound (first-line imaging method) or MRI of the foot in doubtful cases. Management begins with conservative measures (shoe modification + orthopedic insoles + ultrasound-guided corticosteroid infiltration), with a long-term success rate of 50 to 70 %, and continues with surgical neurectomy (removal of the neuroma) for refractory forms, 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
- Predilection 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 + stabbing + electric discharge pain in the forefoot + radiating to the two toes adjacent to the affected space (e.g. 3rd and 4th toes for the 3rd space) + or to the sole of the foot + aggravated by walking on hard ground + prolonged standing + running + wearing narrow or high-heeled shoes + relieved at rest + by removing shoes + and massaging the forefoot | Pain radiating to both toes in a pincer movement (and not to a single dermatome) is characteristic of Morton's neuroma + immediate relief on removal of shoes is a highly suggestive clinical sign. |
| Paraesthesia and numbness of the toes | Tingling + numbness + sensation of a scarf between the toes + or of having a stone in the shoe + involving both toes on either side of the affected space + sometimes permanent in advanced forms. | Bilateral paresthesias in both toes adjacent to the painful space - neurological sign pointing to the digital intermetatarsal nerve |
| Mulder's sign | Lateral compression of the forefoot (squeeze test) - simultaneous pressure on both sides of the foot on the metatarsal heads with one hand + direct compression of the painful interdigital space with the thumb of the other hand → reproduction of the characteristic pain + sometimes perception of a Mulder's «click» (palpable snap when the neuroma moves between the metatarsals) | Positive Mulder's sign → sensitivity 40 to 84 % + specificity 95 to 100 % → most specific clinical sign of all Morton's neuroma semiology |
| Interdigital hypoesthesia | Reduced sensitivity to light touch or pricking in the corresponding interdigital space + or between the two adjacent toes + may be accompanied by reduced discrimination of the two points | Present in 50 to 60 % of confirmed cases + evidence of chronic axonal compression of the digital nerve + confirmatory diagnostic value |
| Associated intermetatarsal bursitis | Inflammation of intermetatarsal bursae, often concomitant with neuroma + swelling + tenderness on direct palpation of dorsal intermetatarsal space + contributes to pain and local nerve compression | Frequently associated with neuroma (50-75 % of cases) + visible on ultrasound as hypoechoic collections + isolated bursitis without neuroma may mimic clinical presentation |
ℹ️
The main differential diagnosis of Morton's neuroma in clinical practice is mechanical stress metatarsalgia (overload of the 2nd or 3rd metatarsals, common after hallux valgus surgery), metatarsal stress fracture (pain on direct palpation of the metatarsal shaft, not the interdigital space), and metatarsophalangeal synovitis or bursitis. Careful clinical examination - in particular, the location of pain on pressure (interdigital space = neuroma; metatarsal head or shaft = mechanical metatarsalgia) and the presence of Mulder's sign - can usually distinguish them 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 the differential diagnosis is difficult + T1 hyposignal and T2 isohyposignal mass in the plantar interdigital space + perineural contrast after gadolinium + more sensitive than ultrasound for small neuromas (< 5 mm) + useful for visualizing associated bursitis + higher cost and 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
- Diagnostic anesthetic 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
Treatment - step-by-step strategy
| Treatment | Procedures and protocol | Success rates and comments |
|---|---|---|
| Shoe modification - mandatory first step | Wide-toe shoes (at least as wide as the foot at its widest point) + low heel (less than 3 cm) + flexible sole + definitive abandonment of pointed-toe and high-heeled shoes + this modification alone improves symptoms in 30 to 50 % mild cases if adopted early in the course of the disease | Fundamental measure + unavoidable + often insufficient on its own in moderate to severe cases + must be systematically combined with all other treatment steps |
| Orthopedic insoles and foot orthotics | Insole with metatarsal bar (metatarsal pad placed behind the metatarsal heads) → redistributes the load towards the metatarsal diaphyses by unloading the heads + insole with depression in the painful interdigital space → reduces direct compression of the nerve + custom-made or semi-custom-made + to be worn continuously in all shoes worn | Symptom reduction of 30 to 50 % in observational studies + to be combined with footwear modifications + better results if neuroma is small and recent + less effective on old, fibrous neuromas |
| Ultrasound-guided corticosteroid infiltration | Injection of long-acting corticosteroid (methylprednisolone 40 mg + triamcinolone 40 mg) + local anesthetic (lidocaine 1 %) in the interdigital space + dorsal or plantar approach + ultrasound guidance strongly recommended for accuracy and efficacy + 1 to 3 infiltrations spaced 4 to 6 weeks apart + to be combined with orthopedic measures | Short-term relief (3 to 6 months) in 50 to 70 % patients + frequent relapses after 6 to 12 months + ultrasound guidance increases the success rate compared with blind injections + no more than 3 injections per year (risk of plantar fat atrophy + planar skin necrosis + rupture of the intermetatarsal ligament) |
| Injections of sclerosing absolute alcohol | Ultrasound-guided perineural injections of absolute alcohol at 4 % (series of 4 to 6 weekly injections) + mechanism: fibrillation and sclerosis of nerve fibers → reduction in neuroma size and pain | Success rate of 60 to 80 % in published series + comparable to surgery in some studies + technique little used in North America but more developed in Europe + lack of high-quality randomized trials + alternative to surgery in patients who refuse general anesthesia |
| Surgical neurectomy (removal of neuroma) | Removal of neuroma and corresponding segment of digital nerve under general or locoregional anesthesia + dorsal approach (most common - incision between metatarsals + section of transverse intermetatarsal ligament + resection of neuroma) or plantar approach (direct access + plantar scar but risk of keloid) + outpatient in most cases + return to walking in wide shoes on Day 1 + full return to activity in 4 to 6 weeks | Complete or very significant relief rate: 85 to 90 % in the long term + nerve resection leaves a permanent hypoesthesia of the corresponding nerve territory (often well tolerated and preferable to pain) + re-growth neuroma on the section stump (recurrence neuroma) in 5 to 10 % of cases → requires re-operation + indicated after failure of 3 to 6 months of well-conducted conservative treatment |
Medical consultation recommended
Medical consultation is recommended for any forefoot pain persisting for more than 4 to 6 weeks despite wearing suitable footwear, particularly if the pain radiates to two adjacent toes, is aggravated by walking and relieved by rest and removal of footwear - the diagnosis of Morton neuroma warrants clinical evaluation and forefoot ultrasound to confirm the diagnosis and exclude a metatarsal stress fracture or other bone pathology before initiating treatment.
For the evaluation of metatarsalgia, prescription of a forefoot ultrasound and X-ray, ultrasound-guided corticosteroid infiltration or referral to an orthopedic surgeon or podiatrist for resistant forms, Clinique Omicron offers medical consultations at its points of service in Quebec and via telemedicine. To book an appointment, visit cliniqueomicron.ca.
Consult at Clinique Omicron
Clinique Omicron's specialized physicians and nurse practitioners (NPs) assess patients presenting with metatarsalgia or forefoot pain suggestive of Morton's neuroma, prescribe musculoskeletal radiography and ultrasound of the foot, initiate appropriate orthopedic advice (shoes + insoles), perform or refer to ultrasound-guided corticosteroid infiltrations, and refer to orthopedic surgeon or podiatrist for forms refractory to conservative treatment. Consultations are available at several points of service in Quebec, and via telemedicine. To book an appointment, visit cliniqueomicron.ca.
The content of this page is provided for informational purposes only and does not replace the advice of a physician, podiatrist or orthopedic surgeon. Diagnosis of Morton's neuroma requires appropriate clinical evaluation and imaging to exclude other forefoot pathologies before initiating treatment.
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