Muscles of lower limb pdf - D. Khalid

Muscles of lower limb

stage

Dr.Kalid Ali Zayer

Fascia lata

Contents
1. Anatomical Structure
2. Anatomical Relations
o 2.1 Iliotibial Tract (ITT)
o 2.2 Tensor Fascia Lata (TFL)
3. Attachments
o 3.1 Proximal
o 3.2 Lateral
o 3.3 Inferior
o 3.4 Central

Fascia

is a sheet or band of fibrous tissue lying deep to the skin. It lines, invests,

and separates structures within the body. There are three main types of fascia:

Superficial fascia

– blends with the reticular layer beneath the dermis.

Deep fascia

– envelopes muscles, bones, and neurovascular structures.

Visceral fascia

– provides membranous investments that suspend organs within

their cavities.

Anatomical Structure

The fascia lata is a deep fascial investment of the musculature of the thigh, and
is analogous to a strong, extensible, and elasticated stocking. It begins proximally
around  the  iliac  crest  and  inguinal  ligament,  and  ends  distal  to  the  bony
prominences of the tibia. It is continuous with what is renamed the deep fascia of
the leg (also known as the crural fascia).
The  depth  of  the  fascia  lata  varies  considerably  across  the  thigh.  It  is  thickest
along  the  superolateral  aspect  of  the  thigh,  where  it  arises  from  the  fascial
condensations  of  gluteus  maximus  and  medius.  It  is  also  thick  around  the  knee
where  the  fascia  receives  reinforcing  fibers  from  tendons  of  the  quadriceps
muscles. The fascial investment is thinnest where it covers the adductor muscles
of the medial thigh.

An  ovoid  hiatus  known  as  the  saphenous  opening  is  present  in  the  fascia  lata
just  inferior  to  the  inguinal  ligament.  The  opening  serves  as  an  entry  point  for
efferent  lymphatic  vessels  and  the  great  saphenous  vein,  draining  into
superficialinguinal  lymph  nodes  and  the  femoral  vein  respectively.

Fig 9 – The ovoid hiatus of the fascia lata.

Anatomical Relations

Iliotibial Tract (ITT)

The iliotibial tract (sometimes known as the iliotibial band or IT band) is a
longitudinal thickening of the fascia lata, which is strengthened superoposteriorly
by fibers from the gluteus maximus. It is located laterally in the thigh, extending
from the iliac tubercle to the lateral tibial condyle. The ITT has three main
functions:

Movement

– acts as an extensor, abductor and lateral rotator of the hip, with an

additional role in providing lateral stabilization to the knee joint.

Compartmentalization

– the deepest aspect of ITT extends centrally to form the

lateral intermuscular septum of the thigh and attaches to the femur.

Muscular sheath

– forms a sheath around the tensor fascia lata muscle.

Tensor Fascia Lata (TFL)

The  tensor  fascia  lata  is  a  gluteal  muscle  that  acts  as  a  flexor,  abductor,  and
internal rotator of the hip. Its name, however, is derived from its additional role in
tensing  the  fascia  lata. It  is  innervated by  the  superior gluteal nerve, like gluteus
medius  and  minimus,  but  is  located  more  anterolaterally  than  the  other  gluteal
muscles. The muscle originates from the iliac crest,  and descends inferiorly to the
superolateral thigh. At the junction of the middle and upper thirds of the thigh, it
inserts into the anterior aspect of the iliotibial tract. When stimulated, the  tensor
fasciae  lata  tautens  the  iliotibial  band  and  braces  the  knee,  especially  when  the
opposite foot is lifted.

Fig 10 – The tensor fascia lata and iliotibial tract.

Gluteal region

Contents
1. The Superficial Muscles
2. The Deep Muscles

The gluteal region is an anatomical area located posteriorly to the pelvic girdle,
at the proximal end of the femur. The muscles in this region move the lower limb
at the hip joint. The muscles of the gluteal region can be broadly divided into two
groups:

Superficial abductors and extenders

– group of large muscles that abduct and

extend the femur. Includes the gluteus maximus, gluteus medius, gluteus
minimus and tensor fascia lata.

Deep lateral rotators

– group of smaller muscles that mainly act to laterally

rotate the femur. Includes the quadratus femoris, piriformis, gemellus superior,
gemellus inferior and obturator internus.
The arterial supply to these muscles is mostly via the superior and inferior gluteal
arteries – branches of the internal iliac artery. Venous drainage follows the
arterial supply.

The Superficial Muscles

The superficial muscles in the gluteal region consist of the three glutei and the
tensor fascia lata. They mainly act to abduct and extend the lower limb at the hip
joint.

Gluteus Maximus

Fig 11 – The superficial muscles of the gluteal region. The gluteus

maximus and medius have been partly removed.

The gluteus maximus is the largest of the gluteal muscles. It is also the most
superficial,producing the shape of the buttocks.

Attachments

: Originates from the gluteal (posterior) surface of the ilium, sacrum

and coccyx. It slopes across the butock at a 45 degree angle, then inserts into the
iliotbial tract and the gluteal tuberosity of the femur.

Actions

: It is the main extensor of the thigh, and assists with lateral rotation.

However, it is only used when force is required, such as running or climbing.

Innervation

: Inferior gluteal nerve.

Gluteus Medius

The gluteus medius muscle is fan-shaped and lies between the gluteus maximus
and the minimus. It is similar in shape and function to the gluteus minimus.

Attachments

: Originates from the gluteal surface of the ilium and inserts into the

lateral surface of the greater trochanter.

Actions

: Abducts and medially rotates the lower limb. During locomotion, it

secures the pelvis, preventing pelvic drop of the opposite limb.

(Note: the posterior fibers of the gluteus medius are also thought to produce a
small amount of lateral rotation).

Innervation

: Superior gluteal nerve.

Gluteus Minimus

The gluteus minimus is the deepest and smallest of the superficial gluteal muscles.
It is similar is shape and function to the gluteus medius.

Attachments

: Originates from the ilium and converges to form a tendon,

inserting to the anterior side of the greater trochanter.

Actions

: Abducts and medially rotates the lower limb. During locomotion, it

secures the pelvis, preventing pelvic drop of the opposite limb.

Innervation

: Superior gluteal nerve.

Tensor Fascia Lata

Tensor fasciae lata is a small superficial muscle which lies towards the anterior
edge of the iliac crest. It functions to tighten the fascia lata, and so abducts and
medially rotates the lower limb.

Attachments

: Originates from the anterior iliac crest, attaching to the anterior

superior iliac spine (ASIS). It inserts into the iliotibial tract, which itself attaches
to the lateral condyle of the tibia.

Actions

: Assists the gluteus medius and minimus in abduction and medial

rotation of the lower limb. It also plays a supportive role in the gait cycle.

Innervation

: Superior gluteal nerve

The Deep Muscles

The deep gluteal muscles are a set of smaller muscles, located underneath the
gluteus minimus. The general action of these muscles is to laterally rotate the
lower limb. They also stabilize the hip joint by ‘pulling’ the femoral head into
the acetabulum of the pelvis.

Piriformis

The piriformis muscle is a key landmark in the gluteal region. It is the most
superior of the deep muscles.

Attachments:

Originates from the anterior surface of the sacrum. It then

travels inferolaterally, through the greater sciatic foramen, to insert into the
greater trochanter of the femur.

Actions

: Lateral rotation and abduction.

Innervation

: Nerve to piriformis.

Obturator Internus

Fig 12 – The deep muscles of the gluteal region.

The obturator internus forms the lateral walls of the pelvic cavity. In some texts,
the obturator internus and the gemelli muscles are considered as one muscle – the
triceps coxae.

Attachments

: Originates from the pubis and ischium at the obturator foramen.

It travels through the lesser sciatic foramen, and attaches to the greater trochanter
of the femur.

Actions

: Lateral rotation and abduction.

Innervation

: Nerve to obturator internus.

The Gemelli – Superior and Inferior

The gemelli are two narrow and triangular muscles. They are separated by the
obturator internus tendon.

Attachments

: The superior gemellus muscle originates from the ischial spine,

the inferior from the ischial tuberosity. They both attach to the greater trochanter
of the femur.

Actions

: Lateral rotation and abduction.

Innervation

: The superior gemellus muscle is innervated by the nerve to

obturator internus, the inferior gemellus is innervated by the nerve to quadratus
femoris.

Quadratus Femoris

The quadratus femoris is a flat, square-shaped muscle. It is the most inferior of the
deep gluteal muscles, located below the gemelli and obturator internus.

Attachments

: It originates from the lateral side of the ischial tuberosity, and

attaches to the quadrate tuberosity on the intertrochanteric crest.

Actions

: Lateral rotation.

Innervation

: Nerve to quadratus femoris.

Fig 13 – The piriformis as an anatomical landmark in the gluteal

region.

Thigh

Contents
1. Iliopsoas
2. Quadriceps Femoris
o 2.1 Vastus Lateralis
o 2.2 Vastus Intermedius
o 2.3 Vastus Medialis
o 2.4 Rectus Femoris
3. Sartorius
4. Pectineus

The musculature of the thigh can be split into three sections; anterior, medial and
posterior. Each compartment has a distinct innervation and function. The muscles
in the anterior compartment of the thigh are innervated by the femoral nerve (L2-
L4), and as a general rule, act to extend the leg at the knee joint. There are three
major muscles in the anterior thigh – the pectineus, sartorius and quadriceps
femoris. In addition to these, the end of the iliopsoas muscle passes into the
anterior compartment.

Iliopsoas

The iliopsoas is actually two muscles, the psoas major and the iliacus. They
originate in different areas, but come together to form a tendon, hence why they
are commonly referred to as one muscle.
Unlike many of the anterior thigh muscles, the iliopsoas does not extend the leg at
the knee joint.

Attachments

: The psoas major originates from the lumbar vertebrae, and the

iliacus originates from the iliac fossa of the pelvis. They insert together onto the
lesser trochanter of the femur.

Actions

: Flexes the thigh at the hip joint.

Innervation

: The psoas major is innervated by anterior rami of L1-3, while the

iliacus is innervated by the femoral nerve.

Fig 14 – The muscles of the anterior thigh.

Quadriceps Femoris

The quadriceps femoris consists of four individual muscles; three vastus muscles
and the rectus femoris. They form the main bulk of the thigh, and collectively are
one  of  the  most  powerful  muscles  in  the  body.  The  muscles  that  form  the
quadriceps  femoris  unite  proximal  to  the  knee  and  attach  to  the  patella  via  the
quadriceps  tendon.  In  turn,  the  patella  is  attached  to  the  tibia  by  the  patella
ligament.  The  quadriceps  femoris  is  the  main  extensor  of  the  knee.

Vastus Lateralis

Proximal attachment:

Originates from the greater trochanter and the lateral lip

of linea aspera.

Actions:

Extends the knee joint and stabilizes the patella.

Innervation:

Femoral nerve.

Vastus Intermedius

Proximal attachment:

Anterior and lateral surfaces of the femoral shaft.

Actions:

Extends the knee joint and stabilizes the patella.

Innervation:

Femoral nerve.

Vastus Medialis

Proximal attachment

: The intertrochanteric line and medial lip of the linea

aspera.

Actions

: Extends the knee joint and stabilizes the patella, particularly due to its

horizontal fibers at the distal end.

Innervation

: Femoral nerve.

Rectus Femoris

Attachments

: Originates from the ilium, just superior to the acetabulum. It

runs straight down the leg (the Latin for straight is rectus), and attaches to the
patella by the quadriceps femoris tendon.

Actions

: The only muscle of the quadriceps to cross both the hip and knee

joints. It flexes the thigh at the hip joint, and extends at the knee joint.

Innervation

: Femoral nerve

Fig 15 – The femur, tibia and patella of the knee joint.

Sartorius

The sartorius is the longest muscle in the body. It is long and thin, running across
the thigh in a inferomedial direction. The sartorius is positioned more superficially
than the other muscles in the leg.

Attachments

: Originates from the anterior superior iliac spine, and attaches to

the superior, medial surface of the tibia.

 Actions

: At the hip joint, it is a flexor, abductor and lateral rotator. At the knee

joint, it is also a flexor.

 Innervation

: Femoral nerve.

Fig 16 – Cross section of the distal thigh. The iliopsoas and pectineus

muscles originate and attach in the proximal thigh, and hence are not

included in this diagram.

Pectineus

The pectineus muscle is a flat muscle that forms the base of the femoral triangle.
It has a dual innervation, and thus can be considered a transitional muscle
between the anterior thigh and medial thigh compartments.

Attachments

: It originates from the pectineal line on the anterior surface of the

pelvis, and attaches to the pectineal line on the posterior side of the femur, just
inferior to the lesser trochanter.

Actions

: Adduction and flexion at the hip joint.

 Innervation

: Femoral nerve. May also receive a branch from the obturator

nerve.

Medial compartment of the thigh

Contents
1. Muscles of the Medial Thigh
o 1.1 Adductor Magnus
o 1.2 Adductor Longus
o 1.3 Adductor Brevis
o 1.4 Obturator Externus
o 1.5 Gracilis

The muscles in the medial compartment of the thigh are collectively known as the
hip  adductors. There are five muscles in this group; gracilis, obturator externus,
adductor  brevis,  adductor  longus  and  adductor  magnus.  All  the  medial  thigh
muscles  are  innervated  by  the  obturator  nerve,  which  arises  from  the  lumbar
plexus. Arterial supply is via the obturator artery.

Muscles of the Medial Thigh

Adductor Magnus

Fig 17 – Muscles of the medial thigh. The overlying muscles in the

anterior compartment have been removed.

The adductor magnus is the largest muscle in the medial compartment. It lies
posteriorly to the other muscles. Functionally, the muscle can be divided into two
parts; the adductor part,and the hamstring part.

Attachments

- Adductor part – Originates from the inferior rami of the pubis and the rami of
ischium, attaching to the linea aspera of the femur.
- Hamstring part – Originates from the ischial tuberosity and attaches to the
adductor tubercle and medial supracondylar line of the femur.

Actions

: They both adduct the thigh. The adductor component also flexes the

thigh, with the hamstring portion extending the thigh.

Innervation

: Adductor part is innervated by the obturator nerve (L2-L4), the

hamstring part is innervated by the tbial component of the sciatc nerve (L4-S3).

Adductor Longus

The adductor longus is a large, flat muscle. It partially covers the adductor brevis
and magnus.
The muscle forms the medial border of the femoral triangle.

Attachments

: Originates from the pubis, and expands into a fan shape, attaching

broadly to the linea aspera of the femur

Actions

: Adduction of the thigh.

Innervation:

Obturator nerve (L2-L4)

Adductor Brevis

Fig 18– View of the medial thigh, with the course of the obturator

nerve highlighted

The adductor brevis is a short muscle, lying underneath the adductor longus. It lies
in between the anterior and posterior divisions of the obturator nerve. Therefore, it
can be used as an anatomical landmark to identify the aforementioned branches.

Attachments

: Originates from the body of pubis and inferior pubic rami. It

attaches to the linea aspera on the posterior surface of the femur, proximal to the
adductor longus.

Actions

: Adduction of the thigh.

Innervation

: Obturator nerve (L2-L4).

Obturator Externus

This is one of the smaller muscles of the medial thigh, and it is located most
superiorly.

Attachments

: It originates from the membrane of the obturator foramen, and

adjacent bone. It passes under the neck of femur, attaching to the posterior aspect
of the greater trochanter.

Actions

: Adduction and lateral rotation of the thigh.

Innervation

: Obturator nerve (L2- L4).

Gracilis

The  gracilis  is  the  most  superficial  and  medial  of  the  muscles  in  this
compartment.  It  crosses  at  both  the  hip  and  knee  joints.  It  is  sometimes
transplanted  into  the  hand  or  forearm  to  replace  a  damaged  muscle.

Attachments

: It originates from the inferior rami of the pubis, and the body of

the pubis.Descending almost vertically down the leg, it attaches to the medial
surface of the tibia,between the tendons of the sartorius (anteriorly) and the
semitendinosus (posteriorly).

Actions

: Adduction of the thigh at the hip, and flexion of the leg at the knee.

Innervation

: Obturator nerve (L2-L4).

Fig 19 – Cross section of the inferior thigh, showing some of the

medial thigh muscles. The adductor brevis and obturator externus

attach superiorly in the thigh, and so are not visible in this cross-

section.

Posterior compartment of the thigh

Contents

1. Muscles in the Posterior Compartment
o 1.1 Biceps Femoris
o 1.2 Semitendinosus
o 1.3 Semimembranosus

The muscles in the posterior compartment of the thigh are collectively known as
the hamstrings. They consist of the biceps femoris, semitendinosus and
semimembranosus,
which form prominent tendons medially and laterally at the back of the knee. As
group, these muscles act to extend at the hip, and flex at the knee. They are
innervated by the sciatic nerve (L4-S3).

Muscles in the Posterior Compartment

The muscles located within the posterior compartment of the thigh are the biceps
femoris, semitendinosus and semimembranosus.
Note: The hamstring portion of the adductor magnus has a similar action to these
muscles, but is located in the medial thigh.

Biceps Femoris

Fig 20 – The muscles of the posterior thigh (right).

Like the biceps brachii in the arm, the biceps femoris muscle has two heads – a
long head and a short head. It is the most lateral of the muscles in the posterior
thigh – the common tendon of the two heads can be felt laterally at the posterior
knee.

Attachments

: The long head originates from the ischial tuberosity of the pelvis.

The short head originates from the linea aspera on posterior surface of the femur.
Together, the heads form a tendon, which inserts into the head of the fibula.

Actions

: Main action is flexion at the knee. It also extends the thigh at the hip,

and laterally rotates at the hip and knee.

Innervation

: Long head innervated by the tibial part of the sciatic nerve, whereas

the short head is innervated by the common fibular part of the sciatic nerve.

Semitendinosus

The semitendinosus is a largely tendinous muscle. It lies medially to the biceps
femoris, and covers the majority of the semimembranosus.

Attachments

: It originates from the ischial tuberosity of the pelvis, and attaches

to the medial surface of the tibia.

Actions

: Flexion of the leg at the knee joint. Extension of thigh at the hip.

Medially rotates the thigh at the hip joint and the leg at the knee joint.

Innervation

: Tibial part of the sciatic nerve.

Semimembranosus

The semimembranosus muscle is flattened and broad. It is located underneath the
semitendinosus.

Attachments

: It originates from the ischial tuberosity, but does so more

superiorly than the semitendinosus and biceps femoris. It attaches to the medial
tibial condyle.

Actions

: Flexion of the leg at the knee joint. Extension of thigh at the hip.

Medially rotates the thigh at the hip joint and the leg at the knee joint.

Innervation

: Tibial part of the sciatic nerve.

Fig 21 – Cross section of the left thigh, showing the position of the

major muscle groups.