The bones of the foot are divided into three groups. The posterior half of the foot is formed by seven tarsal bones.
- The most superior bone is the talus. This has a relatively square-shaped, upper surface that articulates with the tibia and fibula to form the ankle joint. Three areas of articulation form the ankle joint: The superomedial surface of the talus bone articulates with the medial malleolus of the tibia, the top of the talus articulates with the distal end of the tibia, and the lateral side of the talus articulates with the lateral malleolus of the fibula.
- Inferiorly, the talus articulates with the calcaneus (heel bone), the largest bone of the foot, which forms the heel. Body weight is transferred from the tibia to the talus to the calcaneus, which rests on the ground. The medial calcaneus has a prominent bony extension called the sustentaculum tali (“support for the talus”) that supports the medial side of the talus bone.
- The cuboid bone articulates with the anterior end of the calcaneus bone. The cuboid has a deep groove running across its inferior surface, which provides passage for a muscle tendon.
- The talus bone articulates anteriorly with the navicular bone, which in turn articulates anteriorly with the three cuneiform (“wedge-shaped”) bones.
- These bones are the medial cuneiform, the intermediate cuneiform, and the lateral cuneiform. Each of these bones has a broad superior surface and a narrow inferior surface, which together produce the transverse (medial-lateral) curvature of the foot.
The navicular and lateral cuneiform bones also articulate with the medial side of the cuboid bone.
