The hip, or INNOMINATE, is a large ir-
regularly shaped bone composed of three parts:
the ilium, ischium, and pubis. In children these
three parts are separate bones, but in adults they
are firmly united to form a cuplike structure,
called the ACETABULUM, into which the head
of the femur fits. The ILIUM forms the outer
prominence of the hip bone (crest of the ilium),
the ISCHIUM forms the hard lower part, and the
PUBIS forms the front part of the pelvis.
The area where the two pubic bones meet is
called the SYMPHYSIS PUBIS and is often used
in anatomical measurements. The largest foramen
(opening) is located in the hip bone, between the
ischium and the pubis, and is called the OB-
TURATOR FORAMEN. The crest of the ilium
is used in making anatomical and surgical
measurements (e.g., location of the appendix,
which is approximately halfway between the crest
of the ilium and the umbilicus).
The FEMUR, or thigh bone, is the longest
bone in the body. The proximal end is rounded
and has a head supported by a constricted neck
that fits into the acetabulum. Two processes called
the GREATER and LESSER TROCHANTERS
are at the proximal end for the attachment of
muscles. The neck of the femur, located between
the head and the trochanters, is the site most fre-
quently fractured. At the distal end are two bony
prominences called the LATERAL and MEDIAL
CONDYLES, which articulate with the tibia and
The PATELLA is a small oval-shaped bone
overlying the knee joint. It is enclosed within the
tendon of the quadriceps muscle of the thigh.
Bones like the patella that develop within a ten-
don are known as SESAMOID bones.
The TIBIA, or shin bone, is the larger of the
two leg bones and lies at the medial side. The
proximal end articulates with the femur and the
fibula. Its distal end articulates with the talus (one
of the foot bones) and the fibula. A prominence
easily felt on the inner aspect of the ankle is called
the MEDIAL MAL.LEOLUS.
The FIBULA, the smaller of the two leg
bones, is located on the lateral side of the leg,
parallel to the tibia. The prominence at the distal
end forms the outer ankle, known as the
The TARSUS, or ankle, is formed by seven
tarsal bones. The strongest of these is the heel
bone or CALCANEUS.
The sole and instep of the foot is called the
METATARSUS and is made up of five
METATARSAL bones. They are similar in ar-
rangement to the metacarpal of the hand.
The PHALANGES are the bones of the toes
and are similar in number, structure, and arrange-
ment to the bones of the fingers.
Whenever two bones are attached to each
other, a joint is formed. In a freely movable joint,
such as the knee or elbow joint, the ends of the
bones are covered with a smooth layer of car-
tilage. The whole joint is enclosed in a watertight
sac or membrane containing a small amount of
lubricating fluid. This enables the joint to work
with little friction. The ligaments that reach across
the joints from one bone to another keep them
from getting out of place. When ligaments are ac-
cidentally torn, we call the injury a sprain; when
bones are out of place, there is a dislocation; and
when bones are chipped or broken, the injury is
called a fracture.
Joints are classified according to the amount
of movement they permit (fig. 3-23). They may be:
1. IMMOVABLE. Bones of the skull are
rigidly interlocked along immovable joint
lines known as sutures.
Figure 3-23.Typical joints.