Which ligament is the primary restraint to inversion of the subtalar joint?

• A. Deltoid ligament
• B. Interosseous talocalcaneal ligament
• C. Cervical ligament
• D. Spring ligament

Answer: (C)

Inversion stability of the subtalar joint is determined by the ligaments that bind the talus to the calcaneus. The interosseous talocalcaneal ligament sits inside the tarsal canal and acts as the strongest bond between these two bones, effectively preventing the talus from tilting excessively relative to the calcaneus when the hindfoot inverts. This makes it the primary restraint to subtalar inversion. The cervical ligament provides additional support as part of the subtalar ligament complex, but it is not the main limiter of inversion. The deltoid ligament mainly resists eversion of the ankle, and the spring ligament helps maintain the arch and talar stability rather than serving as the primary inversion restraint.