A 45-year-old woman comes to the office with 3 months of right foot pain. Her symptoms started with nighttime numbness at the bottom of the right foot that has progressed to burning and aching pain. She also has vague discomfort while standing or sitting, especially when wearing shoes. The patient has a history of rheumatoid arthritis, which has been stable with weekly etanercept and as-needed ibuprofen. She does not use tobacco, alcohol, or illicit drugs.
Examination shows swollen hand joints without tenderness and mild radial deviation of the wrist. She has mild hallux valgus deformity without focal tenderness on foot examination. Light tapping behind the right medial malleolus elicits tingling. There is intact sensation to light touch and vibration.
Which of the following is the most likely cause of this patient's foot pain?

Question

A 45-year-old woman comes to the office with 3 months of right foot pain.  Her symptoms started with nighttime numbness at the bottom of the right foot that has progressed to burning and aching pain.  She also has vague discomfort while standing or sitting, especially when wearing shoes.  The patient has a history of rheumatoid arthritis, which has been stable with weekly etanercept and as-needed ibuprofen.  She does not use tobacco, alcohol, or illicit drugs.
Examination shows swollen hand joints without tenderness and mild radial deviation of the wrist.  She has mild hallux valgus deformity without focal tenderness on foot examination.  Light tapping behind the right medial malleolus elicits tingling.  There is intact sensation to light touch and vibration.
Which of the following is the most likely cause of this patient's foot pain?

Quizplus · Accepted Answer

This patient's clinical features suggest tarsal tunnel syndrome, which is due to posterior tibial nerve compression as it passes under the flexor retinaculum posterior to the medial malleolus. Tarsal tunnel syndrome is most common following an ankle fracture or dislocation involving the talus, calcaneus, or medial malleolus, in which scar tissue, bony spurs, or bone/cartilage fragments can compress the nerve. Other etiologies include malignancy or inflammatory conditions (eg, rheumatoid arthritis). Patients usually develop pain and paresthesias in the distribution of the nerve (sole of the foot, distal foot, or toes). The pain can radiate up to the heel and calf and is worse at night or with standing. Taking off shoes often relieves the discomfort. Examination can show a positive Tinel's sign (tingling sensation on light percussion over the nerve) and/or sensory loss. Severe nerve injury can lead to atrophy of intrinsic foot muscles. Diagnosis is mainly clinical, although electrodiagnostic testing may be helpful. Treatment includes anti-inflammatory medications (eg, nonsteroidal anti-inflammatory drugs), shoe modification, or corticosteroid injection, with decompressive surgery in refractory cases. (Choice A) Drug-induced neuropathy typically presents with significant bilateral sensory abnormalities and motor weakness. This patient's unilateral presentation and intact sensory examination make this less likely. (Choice B) Morton neuroma presents with numbness or pain between the third and fourth toes and a clicking sensation (Mulder sign) that occurs when simultaneously palpating this space and squeezing the metatarsal joints. Tinel's sign is not a characteristic of Morton neuroma. (Choice C) Plantar fasciitis causes pain and focal tenderness in the plantar area of the rearfoot. The pain may be severe with the first steps of the day. It then often decreases with activity only to worsen again later in the day with prolonged weight bearing. (Choice D) Stress fractures are due to repeated tension or compression without adequate rest that eventually breaks the bone. Patients typically present with sharp and localized pain over a bony surface that is worse with palpation. Educational objective: Tarsal tunnel syndrome presents with pain and paresthesias in the sole of the foot, distal foot, or toes. Examination can show a positive Tinel's sign and/or sensory loss. __________ References: Tarsal tunnel syndrome: A literature review. (http://www.ncbi.nlm.nih.gov/pubmed/22857954)

A 45-Year-Old Woman Comes to the Office with 3 Months