Figure 1. Mortise radiograph of the right ankle.
Figure 2. Lateral radiograph of the right ankle.
A 32-year-old woman presents with a 3-month history of pain in her right medial ankle. The patient denies any known injury or precipitating event that may have caused the ankle pain. Her symptoms are intensified during exercise and when she stands while working as a nurse. Physical examination reveals a pes planus deformity and mild hindfoot valgus. She has poorly localized pain over the posterior medial ankle and heel. Deep palpation of the medial heel causes radiating pain to the plantar aspect of the foot. She also complains of burning pain in the plantar aspect of the foot with the foot in dorsiflexion and eversion. Mortise and lateral radiographs of the patient’s right ankle are obtained (Figures 1 and 2).
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The patient is presenting with symptoms of tarsal tunnel syndrome (TTS). Radiographic imaging does not show evidence of arthritis or deformity. TTS is a compression neuropathy of the tibial nerve at the medial ankle. The tarsal tunnel is formed by the flexor retinaculum and arises medially from the posterior process of the talus and inserts into the calcaneus.1,2
Structures that pass through the tunnel include the tibial nerve, the posterior tibial artery, and the flexor hallucis longus, flexor digitorum longus, and posterior tibialis tendons. Foot and ankle deformities such as pes planus, hindfoot valgus, and forefoot adduction place tension on the tibial nerve and contribute to the neuropathy.1,2
Placing the foot in dorsiflexion and eversion maximally stretches the tibial nerve and may reproduce symptoms of pain. Compression of the tibial nerve at the tarsal tunnel often sends radiating tingling, burning, or numbness to the plantar aspect of the foot where the nerve endings terminate. A positive Tinel sign of radiating symptoms is a valuable provocative test for TTS.
MRI is the imaging modality of choice when TTS is suspected as it closely evaluates the structures of the medial ankle and can identify a space-occupying lesion such as a ganglion cyst, tumor, or osteophyte that may be compressing the tibial nerve. Nerve conduction velocity studies may be helpful after the MRI but may be limited by false negative results.
If no lesion is identified on MRI, first-line treatment of TTS includes immobilization, neuroleptic drugs to manage nerve pain, and nonsteroidal anti-inflammatory drugs to manage pain and inflammation.1,2
Dagan Cloutier, MPAS, PA-C, practices in a multispecialty orthopedic group in the southern New Hampshire region and is editor in chief of the Journal of Orthopedics for Physician Assistants.
1. Wukich DK, Tuason DA. Diagnosis and treatment of chronic ankle pain. Instr Course Lect. 2011;60:335-350.
2. Lareau CR, Sawyer GA, Wang JH, DiGiovanni CW. Plantar and medial heel pain: diagnosis and management. J Am Acad Orthop Surg. 2014;22(6):372-380.