A 23-year-old woman comes to the office due to pain in the right forefoot. The pain started 6 weeks ago and has worsened over the past week. She reports no trauma or inciting event. The pain prevents the patient from doing her usual exercise; she normally runs 3 times a week and occasionally goes hiking. The patient takes no medications and does not use tobacco, alcohol, or illicit drugs. Her last menstrual period was 3 weeks ago, and she is not sexually active. Temperature is 37 C (98.6 F), blood pressure is 100/60 mm Hg, pulse is 70/min, and respirations are 12/min. BMI is 22 kg/m². Physical examination of the right foot elicits a clicking sensation when the third and fourth metatarsal heads are squeezed together; this also produces a burning pain over the plantar surface of the foot. The remainder of the examination is unremarkable. Which of the following is the most likely diagnosis in this patient?

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11ec25c8_d2bf_44e5_bc81_399ecc523b8d_MD0003_00 This patient has chronic forefoot pain consistent with an interdigital (Morton) neuroma. This disorder is not a true neuroma but is a mechanically induced neuropathic degeneration of the interdigital nerves. It is characterized by numbness, aching, and burning in the distal forefoot from the metatarsal heads to the third and fourth toes. Morton neuroma is commonly seen in runners, and symptoms are typically worsened by walking on hard surfaces and wearing tight or high-heeled shoes. neuropathic degeneration of the interdigital nerves The diagnosis of Morton neuroma is primarily made clinically. The pain is often reproduced by lateral compression of the metatarsal heads, and palpation of the third metatarsal interspace during compression may reveal crepitus (Mulder sign). Treatment involves metatarsal support with a bar or padded shoe inserts to decrease pressure on the metatarsal heads. Surgery is usually reserved for patients who fail conservative treatment. (Choice B) Plantar fasciitis causes focal pain in the plantar area of the rearfoot. It usually worsens with the first steps in the morning, decreases with activity during the day, and often worsens again later in the day with prolonged weight bearing. Physical examination shows point tenderness at the plantar surface of the heel. (Choice C) Metatarsal stress fractures are typically seen following an abrupt increase in high-impact activity on hard surfaces. Patients have sharp, localized pain that is reproduced by pressure along the long axis of the bone (axial loading). The female athlete triad (excessive exercise associated with oligomenorrhea, inadequate nutritional intake, and osteopenia/osteoporosis) is a significant risk factor for stress fracture, but this patient has normal BMI and no menstrual irregularities. (Choice D) Tarsal tunnel syndrome is due to compression of the tibial nerve as it passes through the ankle. Patients have burning, numbness, and aching at the distal plantar surface of the foot or toes that may radiate to the calf. The pain is reproduced by percussion over the nerve (Tinel sign), not metatarsal compression. (Choice E) Overuse tendon injuries are common in runners and can involve the anterior tibial, posterior tibial, peroneal, Achilles, or flexor hallucis longus tendons. Patients develop localized pain and swelling in the ankle and hindfoot. Forefoot tendinopathies are less common. Educational objective: Morton neuroma is a mechanically induced degenerative neuropathy that causes numbness, aching, and burning in the distal forefoot from the metatarsal heads to the third and fourth toes. The pain is often reproduced by lateral compression of the metatarsal heads, and palpation of the third metatarsal interspace during compression may reveal crepitus (Mulder sign). Treatment is conservative with metatarsal support or padded shoe inserts. References: The diagnosis and management of Morton's neuroma: a literature review. (http://www.ncbi.nlm.nih.gov/pubmed/23811947)

A 23-Year-Old Woman Comes to the Office Due to Pain