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Tarsals, Metatarsals, and Phalanges (Foot) - Lower Limb

Tarsals, Metatarsals, and Phalanges (Foot) - Lower Limb

The human foot and ankle are strong and complex mechanical structures containing more than 26 bones (tarsals/ankle, metatarsals/mid-bones, and phalanges/toes Figure 1), 33 joints (20 of which are actively articulated), and more than a hundred muscles, tendons, and ligaments.

The foot can be subdivided into the hindfoot, the midfoot, and the forefoot.

The hindfoot is composed of the talus or ankle bone and the calcaneus or heel bone.The two long bones of the lower leg, the tibia and fibula, are connected to the top of the talus to form the ankle.Connected to the talus at the subtalar joint, the calcaneus (the largest bone of the foot) is cushioned inferiorly by a layer of fat.

The five irregular bones of the midfoot (the cuboid, navicular, and three cuneiform bones) form the arches of the foot which serve as shock absorbers.The midfoot is connected to the hind- and fore-foot by muscles and the plantar fascia.

The forefoot is composed of five toes and the corresponding five proximal long bones forming the metatarsus .Similar to the fingers of the hand, the bones of the toes are called phalanges.The big toe has two phalanges, while the other four toes have three phalanges.The joints between the phalanges are called interphalangeal; those between the metatarsus and phalanges are called metatarsophalangeal (MTP).

Both the midfoot and forefoot constitute the dorsum (the area facing upwards while standing) and the planum (the area facing downwards while standing).

The human foot has two longitudinal arches and a transverse arch maintained by the interlocking shapes of the foot bones, strong ligaments, and pulling muscles during activity.The slight mobility of these arches when weight is applied to and removed from the foot makes walking and running more economical in terms of energy.As can be examined in a footprint, the medial longitudinal arch curves above the ground.This arch stretches from the heel bone over the "keystone" ankle bone to the three medial metatarsals.In contrast, the lateral longitudinal arch is very low. With the cuboid serving as its keystone, it redistributes part of the weight to the calcaneus and the distal end of the fifth metatarsal.The two longitudinal arches serve as pillars for the transverse arch which run obliquely across the tarsometatarsal joints.Excessive strain on the tendons and ligaments of the feet can result in fallen arches or flat feet.

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