The muscles acting at the hip joint are listed here according
to their position in relation to the joint. They include several
muscles that act with equal or greater effectiveness at the knee
joint. These are known as the two-joint muscles of the lower extremity.
Only their action at the hip joint is considered in this section.
|Tensor fasciae latae||Six deep outward rotators|
|Adductor brevis||Gluteus medius|
|Adductor longus||Gluteus minimus|
and Functions of Hip Joint Muscles
Iliopsoas (Figure 7.14; Also Listed with the Spinal
Because the psoas major, psoas minor, and iliacus muscles share a common distal
attachment and act as one muscle at the hip joint, the usual practice
of treating them as one muscle is followed here. The muscle is a strong hip flexor. Depending on the
circumstances, it will either flex the thigh
on the trunk or it will flex the trunk
as a unit on the thighs from a supine lying position, or in
any position when the movement is performed against resistance.
Anterior view of pelvic region showing psoas major and
minor, iliacus, and pectineus.
This muscle (Figure 7.14) is a short, thick, quadrilateral muscle
situated lateral and superior to the adductor longus and more or
less parallel to it. It flexes the thigh and
possibly assists in adduction when
the hip is in a flexed state. Whether it also contributes to outward
rotation is debatable. As a flexor it has a good angle of pull that,
together with its internal structure, accounts for its ability to
overcome considerable resistance. It may be palpated at the front
of the pubis, just lateral to the adductor longus, but it is difficult
to distinguish from the latter muscle.
Rectus Femoris (Figure 7.15; Also Listed with the Knee
The rectus femoris muscle is the only quadriceps femoris muscle
that crosses the hip joint. The muscle flexes the
thigh and is also active during abduction and lateral rotation.
It is a large bipenniform muscle, located superficially on the front
of the thigh. It acts on the knee joint as well as the hip and is therefore
a two-joint muscle. It shows maximum activity in single joint movements
or in the countercurrent actions of hip flexion and knee extension.
No activity occurs when the hip flexion is concurrent with knee
flexion. It may be palpated as well as seen on the anterior surface
of the thigh.
Muscles on front of right thigh.
Sartorius (Figure 7.15; Also Listed with the Knee
This muscle is also a two-joint muscle. Its action on the thigh
is flexion. It also shows activity
in abduction when external resistance is offered, and in outward
rotation while sitting.
The sartorius is a long, slender, ribbonlike muscle directed
obliquely downward and medialward across the front of the thigh.
The sartorius muscle is the longest muscle in the body. It is the
most superficial of the anterior thigh muscles and may be readily
seen and palpated on slender subjects. On others, it may be palpated
at the anterior superior iliac spine. Its name derives from its
alleged function of enabling one to sit with the legs crossed, “tailor” fashion.
This muscle (Figures 7.15 and 7.18) flexes and abducts the femur and tenses the fascia lata. It is a small
muscle located close in front of and slightly lateral to the hip
joint, and it may be palpated about 2 inches anterior to the greater
trochanter. Because its pull on the fascia lata is transmitted by
means of the iliotibial tract down to the lateral condyle of the
tibia, it helps extend the leg at the knee. Together with the gluteus
maximus, which also unites with the fascia lata, it helps stabilize
the knee joint in weight-bearing positions. When the lower extremities
are fixed, both of these muscles help steady the pelvis and trunk
on the thighs.
Lateral view of gluteus maximus, tensor fasciae latae,
and iliotibial tract.
The Hamstrings (Figures 7.16 and 7.17; Also Listed with
the Knee Muscles)
The three hamstring muscles—biceps
femoris, semimembranosus, and semitendinosus—are
situated on the back of the thigh, extending from the tuberosity
of the ischium down just below the knee joint, with the biceps femoris
on the lateral aspect of the posterior surface and the two “semi” muscles
on the medial aspect.
Deep posterior muscles of right thigh.
The biceps femoris is the lateral hamstring muscle. Only its
long head crosses the hip joint. The short head, the only one-joint
muscle belonging to the hamstring group, does not cross the hip joint;
therefore, it has no part in hip joint movements. The biceps femoris
tendon may be palpated on the lateral aspect of the posterior surface
of the knee.
Together the semimembranosus and semitendinosus constitute the
medial component of the hamstring group. The semimembranosus lies
anterior to the semitendinosus and has a shorter, deeper tendon
that is extremely difficult to palpate. The semitendinosus tendon
may easily be palpated on the medial aspect of the posterior surface
of the knee when the leg is flexed against resistance from the prone
lying position. It should not be confused with the gracilis tendon,
which lies slightly anterior to it. All three muscles extend the femur or, if the thighs
are bearing weight as in either the standing or long sitting position,
they extend the forward flexed trunk as a unit—that is,
from the hips. (Spinal action must not be confused with hip action,
or vice versa.) The effectiveness of the medial hamstrings as extensors
of the hip is related to knee joint action. There is maximum activity
during hip extension when the knee is either stabilized or flexed
simultaneously (Basmajian and DeLuca 1985). They are inactive, however,
during simultaneous hip and knee extension.
All three hamstrings, in addition to extending the hip, help
stabilize it. Also, they adduct the femur from the abducted position
when the movement is resisted and help rotate the extended femur.
The long head of the biceps femoris rotates the femur laterally
and the inner hamstrings rotates it medially.
This is the largest and most superficial of the three buttock
muscles. It is a potentially powerful hip
extensor. It also rotates the femur
outward when the latter is extended. The lower
portion assists in adduction from an abducted position if the
movement is resisted. The upper portion
abducts against strong resistance. One can understand these
seemingly contradictory functions more readily after studying the
relation of the muscle to the hip joint’s center of motion
as seen from behind. Figure 7.20 shows that roughly one-third of
the muscle lies above the center of motion and two-thirds below
it. This puts the uppermost fibers in a position for abducting the
thigh and the lower fibers in a position for adducting the thigh,
whereas the fibers lying directly behind the femoral head are not
in position for doing either. The entire muscle may easily be palpated
on the posterior surface of the buttock.
Posterior view of gluteus maximus and iliotibial tract.
Diagram showing relation of gluteus maximus to hip joint.
The gluteus maximus has been the subject of much EMG study. Contrary
to what one might think because of its size and prominence, the
gluteus maximus has been shown to be active during the motions named
previously only when moderate to heavy resistance to the movement
exists. And even though it often displays bursts of activity during
brief periods of normal and fast walking, its participation is primarily
as a stabilizer.
The activity of the gluteus maximus in stair climbing has been
confirmed in a number of EMG studies. It has also been found to
be active in walking up an inclined plane, in extending the femur against
resistance, in abducting the femur, especially against resistance
and when rotated outward, and in adducting the femur against resistance
when in an abducted position. This muscle is also most active during
the stance phase of sprint running, as opposed to push-off (Kyrolainen
et al. 2005).
Gluteus maximus activity is also elicited in hyperextension movements
of the thigh performed against resistance from the erect standing
position, muscle setting, and vigorous hyperextension of the trunk
from an erect position. In heavy lifting requiring simultaneous
extension of the hips and knees, the gluteus maximus was found to
be active during the middle to the last 15 to 20 percent of the
movement (Worrell et al. 2001).
The Six Deep
These six muscles (obturator externus and internus, gemellus
superior and inferior, quadratus femoris, and piriformis) (see Figure
7.17) form a compact group behind the hip joint. Their fibers run
horizontally for the most part. The piriformis, the most superior
of the group, is slightly above the joint. The quadratus femoris,
the most inferior, is slightly below it. Some of the muscles have a
secondary function such as abduction or adduction, but neither of
these functions compares in importance with that of outward rotation. They are favorably
situated for helping hold the femoral head in the acetabulum.
This muscle (Figure 7.21) lies just above the adductor longus
and consists of fibers that are almost horizontal when the thigh
is in its normal resting or standing position. From this position
it both adducts and aids
in flexing the femur. If the hip is flexed to a marked degree,
it combines extension with the adduction, against resistance. It
is also active in inward rotation.
Adductor muscles of right thigh.
This muscle (Figure 7.21) adducts and flexes the femur. Steindler (1970)
has pointed out that, though it ordinarily helps flex the thigh,
when the flexion exceeds about 70 degrees it becomes an extensor
as a result of a shift in the relationship between the muscle’s
line of pull and the joint’s center of motion. In an EMG
study in 1966, de Sousa and Vitti found that this muscle was always
active during free adduction and inward rotation (Basmajian and
DeLuca 1985). The muscle may be palpated just below its proximal
attachment at the medial aspect of the groin.
This muscle (Figure 7.21) extends the
thigh as well as adducting it, and the condyloid or lowest portion also assists in inward rotation. De
Sousa and Vitti have noted that this muscle was not active during
free adduction and extension unless the movement was performed against
resistance (Basmajian and DeLuca 1985). Like the other adductors,
it was found to be active in inward rotation. The adductor magnus
may be palpated on the medial aspect of the middle half of the thigh.
The uppermost portion of the muscle—that is, the portion
that comes from the pubis—is sometimes treated as a separate
muscle called adductor minimus.
Gracilis (Figure 7.21; Also Listed with the Knee
This muscle adducts and flexes the femur. As the name indicates,
it is a slender muscle. Being an adductor, it is sometimes called
the adductor gracilis and, like the hamstrings, sartorius, and rectus
femoris, it is a muscle of the knee as well as the hip joint. EMG
studies have shown that it participates in hip flexion only when
the knee is extended and that it is most active during the first
part of flexion: it also helps rotate the femur medially (inward).
This muscle (Figure 7.22a) is essentially an abductor
of the femur. The anterior fibers also
rotate the thigh inward. The muscle may be palpated about 2
or 3 inches above the greater trochanter.
Gluteus medius and minimus.
The muscle is an important one in walking and in standing in
good posture. When the weight is shifted onto one foot, tension
of the gluteus medius and other abductors is an important factor
in stabilization of the hip. Lack of such stabilization results
in an exaggerated sideward thrust of the supporting hip and a drop
of the pelvis on the opposite side, known as Trendelenburg’s
sign. Paralysis or weakness of this muscle causes a typical limping
gait known as the Trendelenburg gait. When the weight is borne on
the affected side, the trunk tilts strongly to that side and the opposite
hip is thrust into prominence.
This muscle (Figure 7.22b) rotates inward
and abducts. It is smaller than the gluteus medius and is situated
beneath it. Whereas the medius is primarily an abductor and secondarily
an inward rotator, the minimus is primarily an inward rotator and secondarily
an abductor. The muscles appear to work cooperatively, each one
assisting in the other’s primary function.
of the Fundamental Movements of the Thigh
This movement is performed chiefly by the tensor fasciae latae,
pectineus (both of these especially during the first half of range),
iliopsoas, rectus femoris, and sartorius. The gracilis and adductors
longus and brevis assist in flexion in selected positions.
The three hamstring muscles are the chief hip extensors. The
gluteus maximus extends only against resistance. The three adductors
also extend against resistance and when the thigh is flexed beyond
a 45-degree angle.
The chief abductors are the gluteus medius and minimus, the former
being the more effective of the two. The sartorius and rectus femoris
are active against resistance; the uppermost fibers of the gluteus
maximus abduct against resistance during the early part of the movement,
and the tensor fasciae latae abducts the thigh when it is extended.
The adductor longus is the primary adductor. Other important
adductors are the adductors magnus and brevis and the gracilis.
The pectineus adducts the flexed thigh, and the lower third of the
gluteus maximus assists in the movement when it is performed against
resistance. The hamstrings adduct the abducted thigh against resistance.
This movement is performed by the six deep outward rotators,
biceps femoris, and gluteus maximus.
The chief inward rotators are the gluteus medius and minimus,
the latter being the more effective of the two. They are assisted
by the semimembranosus, semitendinosus, gracilis, and adductor longus.
The lower fibers of the adductor magnus rotate the thigh inward
when it is extended. Some say that the tensor fasciae latae also
helps, but this is debatable.