Lateral X-ray of the foot.
Figure 1 shows a lateral X-ray of the foot. Which structure does the yellow arrow point to?
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Knowing the complex anatomy of the foot is crucial in differentiating potential pain generators. More than 26 bones make up 3 regions of the foot, including the hindfoot, midfoot, and forefoot. The hindfoot contains the talus and calcaneus, the midfoot contains the navicular, cuboid, and three cuneiform bones, and the forefoot contains the metatarsals and phalanges. The hindfoot and midfoot are separated by the transverse tarsal joint (Chopart joint), and the midfoot and the forefoot by the tarsometatarsal joint.1
The tarsal tunnel is a fibro-osseous canal formed on one side by the medial calcaneus and on the other by the flexor retinaculum. Structures that course through the tunnel include flexor tendons and the neurovascular bundle. The posterior tibial nerve can become entrapped in the tarsal tunnel causing pain and numbness, a condition called tarsal tunnel syndrome.1
The sinus tarsi is a bony canal between the under surface of the talus and the superior surface of the calcaneus, often referred to as the “eye of the foot.” The sinus tarsi can be a source of painful pathology, or a condition known as sinus tarsi syndrome, in which the soft tissue within the sinus tarsi can become inflamed. This can occur after an ankle sprain that causes scar tissue and inflammation to develop within the sinus tarsi.2
The sustentaculum tali is a horizontal shelf of the anterior medial calcaneus that helps support the talus superiorly, provides an attachment site for the plantar calcaneonavicular ligament anteriorly, provides an attachment site for the deltoid ligament medially, and forms the roof of the tarsal tunnel and flexor hallucis longus tendon posterior and inferiorly. The sustentaculum tali can become painful with such conditions as tarsal coalition and fracture.1
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 (JOPA).
- Thompson JC. Netter’s Concise Atlas of Orthopaedic Anatomy. Philadelphia: Elsevier; 2002; 244-279.
- Schubert R. Sinus tarsi syndrome. Radiopaedia. Available at: https://radiopaedia.org/articles/sinus-tarsi-syndrome (Accessed July 24, 2017).