The femur is the only bone in the
leg. The two femurs converge
medially toward the
knees, where they articulate with the
proximal ends of the
tibiae. The angle of convergence of the femora is a major factor in determining the
femoral-tibial angle. Human females have wider
pelvic bones, causing their femora to converge more than in males. In the condition
genu valgum (knock knee) the femurs converge so much that the knees touch one another. The opposite extreme is
genu varum (bow-leggedness). In the general population of people without either genu valgum or genu varum, the femoral-tibial angle is about 175 degrees.
The femur is the longest and, by most measures, the strongest bone in the human body. Its length on average is 26.74% of a person's height,
 a ratio found in both men and women and most
ethnic groups with only restricted variation, and is useful in
anthropology because it offers a basis for a reasonable estimate of a subject's height from an incomplete
The femur is categorised as a
long bone and comprises a
diaphysis (shaft or
body) and two
epiphyses (extremities) that articulate with adjacent bones in the hip and knee.
upper or proximal extremity (close to the
torso) contains the
neck, the two
trochanters and adjacent structures.
head of the femur, which
articulates with the
acetabulum of the
pelvic bone, comprises two-thirds of a
sphere. It has a small groove, or
fovea, connected through the
round ligament to the sides of the
acetabular notch. The head of the femur is connected to the
shaft through the
neck or collum. The neck is 4–5 cm. long and the diameter is smallest front to back and compressed at its middle. The collum forms an angle with the shaft in about 130 degrees. This angle is highly variant. In the
infant it is about 150 degrees and in
old age reduced to 120 degrees on average. An abnormal increase in the angle is known as
coxa valga and an abnormal reduction is called
coxa vara. Both the head and neck of the femur is vastly embedded in the
hip musculature and can not be directly
palpated. In skinny people with the thigh laterally rotated, the head of the femur can be felt deep as a resistance
profound (deep) for the
The transition area between the head and neck is quite rough due to attachment of muscles and the
hip joint capsule. Here the two
lesser trochanter, are found. The greater trochanter is almost box-shaped and is the most
lateral prominent of the femur. The highest point of the greater trochanter is located higher than the collum and reaches the midpoint of the
hip joint. The greater trochanter can easily be felt. The
trochanteric fossa is a deep depression bounded posteriorly by the intertrochanteric crest on medial surface of the greater trochanter. The lesser trochanter is a cone-shaped extension of the lowest part of the femur neck. The two trochanters are joined by the
intertrochanteric crest on the back side and by the
intertrochanteric line on the front.
A slight ridge is sometimes seen commencing about the middle of the intertrochanteric crest, and reaching vertically downward for about 5 cm. along the back part of the body: it is called the
linea quadrata (or quadrate line).
About the junction of the upper one-third and lower two-thirds on the intertrochanteric crest is the
quadrate tubercle located. The size of the tubercle varies and it is not always located on the intertrochanteric crest and that also adjacent areas can be part of the quadrate tubercel, such as the posterior surface of the greater trochanter or the neck of the femur. In a small anatomical study it was shown that the
epiphysial line passes directly through the quadrate tubercle.
body of the femur (or shaft) is long, slender and almost cylindrical in form. It is a little broader above than in the center, broadest and somewhat flattened from before backward below. It is slightly arched, so as to be convex in front, and concave behind, where it is strengthened by a prominent longitudinal ridge, the
linea aspera which diverges proximal and distal as the medial and lateral ridge. Proximal the lateral ridge of the linea aspera becomes the
gluteal tuberosity while the medial ridge continues as the
pectineal line. Besides the linea aspera the shaft has two other bordes; a
lateral and medial border. These three bordes separates the shaft into three surfaces: One
anterior, one medial and one lateral. Due to the vast
musculature of the thigh the shaft can not be
third trochanter is a bony projection occasionally present on the proximal femur near the superior border of the gluteal tuberosity. When present, it is oblong, rounded, or conical in shape and sometimes continuous with the gluteal ridge.
 A structure of minor importance in humans, the incidence of the third trochanter varies from 17–72% between ethnic groups and it is frequently reported as more common in females than in males.
Lower extremity of right femur viewed from below.
from behind, showing interior ligaments.
lower extremity of the femur (or distal extremity) is larger than the
upper extremity. It is somewhat cuboid in form, but its transverse diameter is greater than its antero-posterior (front to back). It consists of two oblong eminences known as the
Anteriorly, the condyles are slightly prominent and are separated by a smooth shallow articular depression called the patellar surface. Posteriorly, they project considerably and a deep notch, the
Intercondylar fossa of femur, is present between them. The
lateral condyle is the more prominent and is the broader both in its antero-posterior and transverse diameters. The
medial condyle is the longer and, when the femur is held with its body perpendicular, projects to a lower level. When, however, the femur is in its natural oblique position the lower surfaces of the two condyles lie practically in the same horizontal plane. The condyles are not quite parallel with one another; the long axis of the lateral is almost directly antero-posterior, but that of the medial runs backward and medialward. Their opposed surfaces are small, rough, and concave, and form the walls of the
intercondyloid fossa. This fossa is limited above by a ridge, the
intercondyloid line, and below by the central part of the posterior margin of the patellar surface. The
posterior cruciate ligament of the
knee joint is attached to the lower and front part of the medial wall of the fossa and the
anterior cruciate ligament to an impression on the upper and back part of its lateral wall.
The articular surface of the lower end of the femur occupies the anterior, inferior, and posterior surfaces of the condyles. Its front part is named the patellar surface and articulates with the
patella; it presents a median groove which extends downward to the
intercondyloid fossa and two convexities, the lateral of which is broader, more prominent, and extends farther upward than the medial.
Each condyle is surmounted by an elevation, the
medial epicondyle is a large convex eminence to which the
tibial collateral ligament of the knee-joint is attached. At its upper part is the
adductor tubercle and behind it is a rough impression which gives origin to the medial head of the
lateral epicondyle which is smaller and less prominent than the medial, gives attachment to the
fibular collateral ligament of the
The femur develops from the
limb buds as a result of interactions between the
ectoderm and the underlying
mesoderm, formation occurs roughly around the fourth week of development.
By the sixth week of development, the first
hyaline cartilage model of the femur is formed by
Endochondral ossification begins by the end of the
embryonic period and primary
ossification centers are present in all long bones of the limbs, including the femur, by the 12th week of development. The
hindlimb development lags behind
forelimb development by 1–2 days.