Morton's Neuroma

Morton's neuroma is a condition where the **interdigital nerve** — the nerve that runs between the metatarsal bones (the long bones of the forefoot) — becomes irritated, compressed, and surrounded by thickened fibrous tissue. This creates a painful, enlarged area of nerve tissue in the ball of the foot. **The anatomy:** Your foot has interdigital nerves that run between each pair of metatarsal bones, providing sensation to the toes. These nerves pass through a tight space between the metatarsal heads (the rounded ends of the bones that form the ball of the foot). When the metatarsal heads are squeezed together — by tight shoes, high heels, or foot deformities — the nerve is compressed and irritated. **The process:** 1. The nerve is repeatedly compressed between the metatarsal heads 2. Chronic irritation causes the tissue AROUND the nerve (the perineurium) to thicken and scar 3. The thickened tissue compresses the nerve further, creating a vicious cycle 4. The nerve becomes inflamed and painful — producing the characteristic burning, shooting pain Despite its name, Morton's neuroma is **NOT a tumor** and NOT cancerous. The term "neuroma" is a misnomer — it's actually **perineural fibrosis** (scarring around the nerve). The name comes from **Thomas George Morton** (1835-1903), an American surgeon who described the condition in 1876. **Why between the 3rd and 4th toes?** The third interdigital nerve is anatomically unique — it receives contributions from BOTH the medial plantar nerve and the lateral plantar nerve, making it **thicker than the other interdigital nerves**. This larger size makes it more susceptible to compression in the tight space between the metatarsal heads. Morton's neuroma is commonly confused with [plantar fasciitis](/condition/plantar-fasciitis) — but the pain locations are different. Morton's neuroma causes pain in the **ball of the foot** (forefoot), while [plantar fasciitis](/condition/plantar-fasciitis) causes pain in the **heel** (hindfoot). Understanding this difference is crucial for proper treatment.

The development of Morton's neuroma is primarily a story of **mechanical compression and chronic nerve irritation:** **Footwear (the #1 modifiable risk factor):** - **High heels**: Every 1-inch increase in heel height increases forefoot pressure by **22%**. A 3-inch heel shifts **75% of body weight** onto the ball of the foot, directly compressing the interdigital nerves - **Narrow toe boxes**: Force the metatarsal heads together, squeezing the nerve - **This explains the 8-10:1 female-to-male ratio** — women's fashion footwear creates the perfect conditions for nerve compression - Simply switching to wide-toe-box, low-heeled shoes resolves symptoms in **40-50%** of mild cases without any other treatment **Foot biomechanics:** - **Excessive pronation** (foot rolling inward): Stretches the nerve with each step, increasing irritation - **High arches (pes cavus)**: Concentrate pressure on the ball of the foot rather than distributing it across the entire sole - **Flat feet (pes planus)**: Alter forefoot mechanics and nerve tension - **Bunions and hammertoes**: Change the alignment of the metatarsal heads, creating abnormal nerve compression - **Tight calf muscles**: Force more weight-bearing onto the forefoot during gait **Activity-related:** - **Running**: The forefoot absorbs **2-3 times body weight** with each stride. Repetitive impact accumulates microtrauma to the nerve. - **Court sports** (tennis, basketball, squash): Rapid start-stop movements and pivoting compress the forefoot - **Climbing and squatting**: Sustained forefoot compression - **Ballet and dance**: Extreme plantar flexion and forefoot loading **The anatomic predisposition (3rd web space):** The third interdigital nerve is uniquely vulnerable because: 1. It receives a communicating branch from both plantar nerves, making it **thicker** 2. The 3rd and 4th metatarsals have greater relative mobility than the 2nd and 3rd, creating more shear force on the nerve 3. The transverse metatarsal ligament is tightest in this area, creating a rigid floor that the nerve gets pressed against **Why it becomes chronic:** Once perineural fibrosis develops, the thickened tissue itself becomes a space-occupying lesion that perpetuates nerve compression — even in wider shoes. This is why early intervention (before significant fibrosis) has much better outcomes.

**First-line: Conservative treatment (effective in 80% of patients):** **1. Footwear modification (the MOST important step):** - Wide-toe-box shoes with at least **1/2 inch of space** beyond the longest toe - Heel height **under 1 inch (2.5 cm)** — lower is better - Firm, supportive sole to reduce forefoot flexion - Brands designed for wide forefeet: Altra, Hoka, New Balance (wide widths), Keen - Simply changing shoes resolves symptoms in **40-50%** of mild cases **2. Metatarsal pad (met pad):** - A dome-shaped pad placed just BEHIND (proximal to) the metatarsal heads - Spreads the metatarsal bones apart, taking pressure off the nerve - **Should NOT be placed under the metatarsal heads** — this worsens compression - Available as adhesive pads or built into orthotics - Provides relief in **50-70%** of patients **3. Custom orthotics:** - Full-length orthotic with integrated metatarsal pad and arch support - Controls excessive pronation and redistributes forefoot pressure - Most effective for patients with underlying biomechanical issues (flat feet, high arches) **4. Corticosteroid injection:** - Injection of corticosteroid + local anesthetic into the intermetatarsal space - Provides significant relief in **30-50%** of patients - Can be repeated 2-3 times (spaced 4-6 weeks apart) - Diminishing returns with repeated injections; risk of fat pad atrophy with excessive use **5. Alcohol sclerosing injections (emerging treatment):** - Series of 4-7 injections of **4% alcohol** into the neuroma every 1-2 weeks - Causes controlled nerve degeneration, reducing pain signals - **60-80% success rate** in recent studies — may be an alternative to surgery - Less studied than corticosteroid but growing evidence base **Surgical treatment (for the 20% who fail conservative care):** - **Neurectomy**: Surgical removal of the affected nerve segment — the standard procedure - Performed through a dorsal (top of foot) or plantar (sole) incision - **80-85% good to excellent outcomes** - Expected side effect: **permanent numbness** in the affected toes (the nerve is removed) - **15-20%** experience recurrent symptoms, stump neuroma, or persistent numbness - Recovery: Weight-bearing in a surgical shoe for 2-3 weeks; return to regular shoes in 4-6 weeks **Newer treatments:** - **Radiofrequency ablation**: Thermal destruction of the nerve without surgery — emerging evidence - **Cryotherapy (cryoablation)**: Freezing the nerve — small studies show 75-80% improvement - **Shockwave therapy**: Extracorporeal shockwave — limited evidence but promising early results