Morton's Neuroma
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Direct answer
Morton's neuroma is a burning forefoot pain in the third webspace — between the third and fourth metatarsal heads — that forces the patient to remove the shoe and rub the foot, because tight footwear compresses an already-irritated common digital nerve. It is not a true neuroma at all: chronic compression under the deep transverse metatarsal ligament produces perineural fibrosis and degeneration, a misnomer examiners enjoy probing. Diagnosis is clinical — webspace tenderness with a Mulder click — supported by ultrasound; footwear modification and a metatarsal dome pad help a majority, and dorsal neurectomy is the definitive option after conservative care fails, at the price of permanent numbness in the adjacent toes.
What you must remember
- Third webspace commonest, second space next; the classic anatomic explanation is the communicating branch between the medial and lateral plantar nerves, which sits most often in the third interspace and thickens that common digital nerve.
- Pathology: perineural fibrosis and axonal degeneration of the common digital nerve beneath the deep transverse metatarsal ligament — no Schwann cells, no capsule, hence "neuroma" is a misnomer.
- Clinical triad: burning pain radiating into the affected toes, worse in tight shoes and on walking, relieved by taking the shoe off and massaging; Mulder click — thumb-finger squeeze of the metatarsal heads with plantar thumb pressure producing a palpable, sometimes audible click and the familiar pain.
- Differentials to exclude at the bedside: MTP synovitis (tenderness at the joint line, pain on toe dorsiflexion), second metatarsal stress fracture, Freiberg infraction (adolescent second MTP), plantar plate tear (toe deviation, drawer instability), intermetatarsal bursitis.
- Investigations: ultrasound shows a non-compressible hypoechoic ovoid mass in the interspace and is the practical first test; MRI is more sensitive but rarely changes management; radiographs only exclude stress fracture and Freiberg.
- Non-surgical ladder: wide toe-box footwear, metatarsal dome pad placed proximal to the metatarsal heads (it splays the interspace), local anaesthetic-steroid injection into the webspace, orthotics — most patients settle.
- Surgery: dorsal approach neurectomy of the common digital nerve; permanent numbness in the touching sides of the two toes is consented, and stump neuroma recurrence — pain returning months later because the nerve was cut too far distally — occurs in up to a fifth; a plantar approach gives direct exposure but risks a painful plantar scar.
- Indian practice reality: narrow fashion footwear in women and stiff pointed occupational shoes in men fill the clinic; footwear counselling is the treatment the exam wants first.
Webspace workup
A 45-year-old woman reports three years of forefoot burning, worst in her office shoes, with an electric jolt into the third and fourth toes. Palpation reproduces tenderness in the third interspace rather than on a metatarsal head, the Mulder click is present, and toe dorsiflexion — the MTP synovitis provocation — is painless, which steers away from joint pathology. Radiographs are normal; a webspace injection abolishes the pain for the afternoon — diagnostic and therapeutic in one needle. Conservative care runs three to six months: wide shoes, dome pad, a second injection if the first faded. Surgery, when pain persists, carries two consent points the examiner will chase: the toes stay permanently numb on their touching sides, and a nerve resected too far distally can recur as a painful stump neuroma.
Why the misnomer matters
Examiners probe "what does the histopathology show?" expecting perineural fibrosis and degeneration — not Schwann cells or a capsule — and then "why the third space?", expecting the communicating branch between the medial and lateral plantar nerves, present in most feet, which thickens the third common digital nerve and jams it against the ligament with every step. The deeper lesson is that webspace pain is a differential diagnosis, not a diagnosis: synovitis, stress fracture, Freiberg and plantar plate tear all live in the same centimetre of foot, each with a bedside test that separates it.
Frequently asked questions
Why is Morton's neuroma called a neuroma if it is not one?
Histology shows perineural fibrosis and degeneration of the common digital nerve from chronic compression — there is no true neural tumour, capsule or Schwann cell proliferation.
What is Mulder's sign?
Pain and a palpable click produced by squeezing the metatarsal heads while pressing up from the plantar side — the click is the displaced nerve escaping between the heads.
Which investigations help, and when?
Ultrasound first for the hypoechoic interspace mass; MRI if the diagnosis is unclear; radiographs only to exclude stress fracture and Freiberg infraction.
What must be consented before neurectomy?
Permanent numbness on the touching sides of the adjacent toes, and the possibility of a painful stump neuroma if the nerve is divided too distally.
Where is the metatarsal pad placed and why?
Proximal to the metatarsal heads — it spreads the interspace, unloading the compressed nerve with each step.