Section II. LOWER EXTREMITY
The bones of the lower extremity may be divided into four groups:
a. The Pelvic Girdle. The pelvic girdle is composed of the two os coxae (hip
bones), the sacrum, and the coccyx. The sacrum and coccyx are also considered as
part of the vertebral column.
b. The Thigh. The bone of the thigh is the femur, a long bone extending
between the hip and the knee. The patella, or kneecap, is included here for
c. The Leg. The leg extends from the knee to the ankle and consists of the
tibia, or shin bone (medial portion), and the fibula, or calf bone (lateral portion).
d. The Foot. The foot may be divided into three groups of bones: the tarsus
(seven tarsal bones); the metatarsus or foot proper (five metatarsal bones); and the
digits or toes (14 phalanges).
2-10. THE FOOT (figure 2-11)
a. The Tarsus. The tarsus is composed of seven bones, referred to collectively
as the tarsal bones. The tarsal bones may be divided into two-groups: the proximal
region consisting of the calcaneus, the talus, and the navicular; and a distal row (named
from medial to lateral) consisting of the first, second, and third cuneiform bones and the
(1) The calcaneus (os calcis) or heel bone is the largest of the tarsal bones.
Its large posterior end forms the heel, and is marked by an expanded portion, the
(2) The talus (astragalus) is the second largest of the tarsal bones. It
consists of a body, a head, and a neck. The superior aspect of the body presents an
articular surface, called the trochlea. The head is the rounded anterior end which is
received into the posterior concavity of the navicular bone.
(3) The navicular bone is somewhat boat-shaped. It is situated on the
medial side of the foot between the talus posteriorly and the cuneiform bones anteriorly.
Posteriorly, it presents an oval, concave surface for articulation with the rounded head
of the talus.