Human Anatomy - Kotsan I. Ya. 2009

Skeleton of the lower limb
Tarsal bones

The tarsus in humans, as in other primates, consists of seven bones characterized by considerable massiveness, which is associated with the heavy load applied to the posterior part of the FOOT in an upright posture. The Tarsal Bones are arranged in two rows: proximal and distal. The proximal row is formed by the talus and calcaneus, while the distal (anterior) row consists of the navicular, cuboid, and three cuneiform bones (medial, intermediate, and lateral).

The talus is located between the leg and the calcaneus. Its posterior part is called the body of the talus (corpus tali), followed by a narrowed section — the neck of the talus (collum tali), which separates the body from the anteriorly directed HEAD of the talus (caput tali). The head features a spherical navicular articular surface (facies articularis navicularis) anteriorly, which serves for articulation with the navicular bone. Superiorly on the body is the trochlea of the talus (trochlea tali), which has three surfaces: superior, medial malleolar, and lateral malleolar. The superior surface (facies superior) of the trochlea is designed to articulate with the inferior articular surface of the Tibia. The medial malleolar surface (facies malleolaris medialis) and lateral malleolar surface (facies malleolaris lateralis) articulate with the corresponding articular surfaces of the malleoli. Laterally on the body of the trochlea is the lateral process of the talus (processus lateralis tali), and posteriorly is the posterior process of the talus (processus posterior tali), which is divided by the groove for the tendon of the flexor hallucis longus Muscle (sulcus tendinis musculi flexoris hallucis longi) into a medial tubercle (tuberculum mediale) and a lateral tubercle (tuberculum laterale). On the inferior aspect of the talus, there are three articular surfaces for articulation with the calcaneus: the anterior talar articular surface (facies articularis calcanea anterior), middle talar articular surface (facies articularis calcanea media), and posterior talar articular surface (facies articularis calcanea posterior). Between the middle and posterior articular surfaces lies the talar sulcus (sulcus tali), which together with the calcaneal sulcus forms the tarsal sinus (sinus tali).

The calcaneus is the largest bone in the human foot. It is located beneath the talus and projects significantly backward from under it. The body of the calcaneus ends posteriorly in the calcaneal tuberosity (tuber calcanei), which on its plantar aspect has two prominences: the medial process of the calcaneal tuberosity (processus medialis tuberis calcanei) and the lateral process of the calcaneal tuberosity (processus lateralis tuberis calcanei). Superiorly, the calcaneus features the anterior talar articular surface (facies articularis talaris anterior), the middle talar articular surface (facies articularis talaris media), and the posterior talar articular surface (facies articularis talaris posterior), which form joints with the talus. Between the middle and posterior articular surfaces is the calcaneal sulcus (sulcus calcanei), which together with the corresponding sulcus on the talus forms a canal — the tarsal sinus, the entrance to which is located on the DORSAL SIDE OF the foot laterally. A short and thick process — the sustentaculum tali — extends from the anterosuperior margin of the calcaneus and Supports the head of the talus. Below the sustentaculum tali runs the groove for the tendon of the flexor hallucis longus muscle (sulcus tendinis musculi flexoris hallucis longi). On the lateral aspect of the calcaneus is the groove for the tendon of the peroneus (fibularis) longus muscle (sulcus tendinis musculi peronei (fibularis) longi), which is bounded superiorly by the fibular (peroneal) trochlea (trochlea peronealis (fibularis)). At the anterior end of the calcaneus is the cuboid articular surface (facies articularis cuboidea), designed for articulation with the cuboid bone.

The navicular bone (os naviculare) is located on the medial margin of the foot, anterior to the talus, posterior to the cuneiform bones, and medial to the cuboid bone. Posteriorly, the navicular bone has a concave talar articular surface (facies articularis tali) that serves to articulate with the head of the talus, and anteriorly, a cuneiform articular surface (facies articularis cuneiformia) divided into three articular facets for articulation with the three cuneiform bones. On the medial side of the bone is the tuberosity of the navicular bone (tuberositas ossis navicularis) — the attachment site for the tibialis posterior muscle. On the lateral side of the navicular bone, there may be a small, inconstant cuboid articular surface (facies articularis cuboidea) intended for connection with the cuboid bone.

The cuboid bone (os cuboideum) is situated on the lateral side of the foot between the calcaneus and the bases of the IV and V Metatarsal Bones. The posterior surface of the bone features a saddle-shaped articular surface for articulation with the calcaneus. The anterior surface contains an articular surface divided by a crest for articulation with the IV and V metatarsal bones. On the medial side of the bone are articular surfaces for articulation with the lateral cuneiform and navicular bones. On the inferior (plantar) surface of the bone is the tuberosity of the cuboid bone (tuberositas ossis cuboidea), anterior to which runs the groove for the tendon of the peroneus (fibularis) longus muscle (sulcus tendinis musculi peronei (fibularis) longi).

The cuneiform bones (ossa cuneiformia) are located on the medial margin of the foot between the navicular bone and the bases of the I–III metatarsal bones, possessing articular surfaces to articulate with them. The largest of the cuneiform bones is the medial cuneiform bone (os cuneiforme mediale), which on its concave lateral side also bears articular surfaces for articulation with the intermediate cuneiform bone and the second metatarsal. The wide part (Base of the wedge) of the medial cuneiform bone is directed downward (toward the sole), and the narrow part upward, whereas in the remaining bones, the arrangement is reversed. The intermediate cuneiform bone (os cuneiforme intermedium) is the smallest. On its medial side, it has an articular surface to articulate with the medial cuneiform bone, and on its lateral side, an articular surface to articulate with the lateral cuneiform bone. The lateral cuneiform bone (os cuneiforme laterale) has articular surfaces that connect it on the medial side with the intermediate cuneiform bone and the base of the second metatarsal bone, and on the lateral side with the cuboid bone.

The cuneiform bones, together with the cuboid bone and the bases of the metatarsal bones, participate in forming the arch of the foot, which is oriented with its convex part facing upward and its concave part downward.