Each foot is made up of
twenty-six bones which form the ankle,
top and bottom of the foot, and toes. These bones are articularly
specialized, allowing a wide range of flexibility, while being able to
withstand the incredible amounts of stress placed upon them. It is
estimated that each stride of an adult places 900 pounds per square inch
on the bottom of the foot. Seven of these bones form the compact
arrangement of the ankle,
or tarsus,
and the heel. These tarsal bones include the navicular,
the three cuneiform, the cuboid, the talus,
and the calcaneus (which also forms the heel) bones. These
tarsal bones are arranged generally in two rows, the proximal (nearer
the body) and distal (nearer the toes). The distal tarsals
articulate
with the five metatarsals. The long metatarsals form the broad,
long structure of the foot, as seen in the superior view. These,
in turn, articulate with the proximal phalanges (toe bones).
The proximal phalanges join with the middle phalanges, which articulate
with the end sections of the toes, called distal phalanges.
The large toe is the exception, as it lacks a middle phalanx. Ligaments
connect the bones of the foot together and allow the muscles of the calf
to remotely influence these bones.
Tarsals: The calcaneus bone forms the lower, outer part of the ankle and extends downward to form the heel. It is responsible for bearing much of the immediate stress placed upon the foot during walking. This bone is also called the calcaneum.
The cuboid bone forms the outer portion of the tarsus (ankle) in the foot. It articulates with the outer metatarsals, the lateral cuneiform, and the calcaneus. It is so named because of its roughly cubic shape.
Three cuneiform bones are located in the tarsus, or ankle: the intermediate, the lateral, and the medial. So named because of their wedge shape (cuneus means "wedge") the cuneiform bones form, with the cuboid bone, the distal row of the tarsals. The three cuneiforms articulate with the navicular, cuboid, and metatarsal bones.
The navicular bone of the foot is one of the proximal three bones of the tarsus, or ankle. It articulates with the calcaneus, the talus, and the three cuneiform bones. Its name derives from its boat-like shape.
The talus is one of the three distal bones of the tarsus, or ankle. It articulates with the calcaneus, the navicular, the tibia, and the fibula bones. The talus, or astralagus, forms much of the high, inside, ankle structure.
The foot features five long bones which extend between the tarsals of the ankle and the phalanges (toe bones). The metatarsals are numbered beginning with that of the large toe (#1). The head (distal end) of each metatarsal bone is bulbous at the site of articulation with the phalanges, and features small projections or knobs to which the ligaments of the toes and foot attach.
The bones of the toes (and fingers) are known as phalanges (singular
: phalanx). Each toe has three phalanges, with the exception of the
large toe, which has only two. The phalanges are referred to by their
position with respect to the body when the foot is extended. The
bones at the ends of the toes, because they are the most distant from the
body, are the distal
phalanges. The next are the middle phalanges (which the large
toe does not have). Those articulating with the metatarsals of the
foot are the proximal phalanges. The ends of each phalanx are somewhat
bulbous at the site of articulation with other bones. These prominences
also serve as sites of attachment for phalangeal ligaments.