The Muscular System
The muscles ﬂeshing out the thigh are difﬁcult to segregate into
groups on the basis of action. Some thigh muscles act only at the
hip joint, others only at the knee, while still others act at both
muscles of the hip and thigh ﬂex
the femur at the hip and extend the leg at the knee, producing the
foreswing phase of walking. The
muscles of the hip and
thigh, by contrast, mostly extend the thigh and ﬂex the leg—the
backswing phase of walking. A third group of muscles in this region,
, muscles, all adduct the thigh; they have no
effect on the leg.
In the thigh, the anterior, posterior, and adductor muscles are
separated by walls of fascia into
(see Figure 10.26a). The deep fascia of the thigh, the
, surrounds and encloses all three groups of muscles like
a support stocking.
Movements of the thigh (occurring at the hip joint) are
accomplished largely by muscles anchored to the pelvic girdle. Like
the shoulder joint, the hip joint is a ball-and-socket joint permitting
ﬂexion, extension, abduction, adduction, circumduction, and
rotation. Muscles effecting these movements are among the most
powerful muscles of the body.
For the most part, the thigh
pass in front of the hip
joint. The most important thigh ﬂexors are the
tensor fasciae latae
They are assisted in this action by the
medial thigh and the straplike
is effected primarily by the massive
of the posterior thigh (Figure 10.21a). During forceful
of the buttocks is called into play.
Buttock muscles that lie lateral to the hip joint (
the thigh (Figure 10.21c).
Thigh adduction is the role of the adductor muscles of the medial
thigh. Abduction and adduction of the thighs are extremely important
during walking to shift the trunk from side to side and balance the
body’s weight over the limb that is on the ground. Many different
muscles bring about medial and lateral rotation of the thigh.
At the knee joint, ﬂexion and extension are the main movements.
The sole knee
muscle of the
anterior thigh, the most powerful muscle in the body (Figure 10.20a).
The quadriceps is antagonized by the hamstrings of the posterior
compartment, which are the prime movers of knee ﬂexion.
Table 10.17 (Part I) summarizes the actions of these muscles.
Muscles Crossing the Hip and Knee Joints: Movements of the Thigh and Leg
(Figures 10.20 and 10.21)
ORIGIN (O) AND
PART I: ANTERIOR AND MEDIAL MUSCLES
Origin on the Pelvis or Spine
Iliopsoas is a composite of two closely related muscles (iliacus and psoas major) whose ﬁbers pass under the
inguinal ligament (see Figure 10.12) to insert via a common tendon on the femur.
Large, fan-shaped, more
O—iliac fossa and crest,
ala of sacrum
of femur via iliopsoas
Iliopsoas is the
mover for ﬂexing thigh,
or for ﬂexing trunk on
as during a bow
Longer, thicker, more
medial muscle of the pair
(butchers refer to this
muscle as the tenderloin)
O—by ﬂeshy slips from
bodies, and discs of
lumbar vertebrae and T
of femur via iliopsoas
As above; also ﬂexes
vertebral column laterally
Ventral rami (L
Straplike superﬁcial muscle
running obliquely across
anterior surface of thigh
to knee; longest muscle in
body; crosses both hip and
O—anterior superior iliac
I—winds around medial
aspect of knee and
inserts into medial aspect
of proximal tibia
Flexes, abducts, and
laterally rotates thigh
ﬂexes knee (weak) as in a
soccer kick; helps produce
the cross-legged position