Middle facet coalition of the subtalar joint may result in what type of ankle joint?

• A. Normal ankle joint
• B. Ball-and-socket type ankle joint
• C. Hinged ankle joint
• D. Congruent ankle mortise

Answer: (B)

The key idea is that fusing the middle facet of the subtalar joint changes how the talus articulates with the calcaneus, turning the hindfoot contact into a more spherical, ball-and-socket style arrangement. When the middle facet coalites, the subtalar joint loses its normal glide and tilt patterns; the remaining articular surfaces across the subtalar region and the way the talus sits within the mortise produce a more convex-to-concave, ball-and-socket–like contact. That shift allows motion around multiple axes in the ankle area, rather than just a hinge motion, so the ankle joint is described as ball-and-socket rather than purely hinge.