Muscles of the Thigh

Muscles of the Thigh

6.1 Identify, describe the attachments of and deduce the actions of the muscles of the

thigh:

Anterior group

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Sartorius:

This is a long strap like muscle with flattened tendons at each end

It is the most superficial muscle in the anterior group and runs

across all muscles lateral to medial

It is the longest muscle in the body

The upper attachment is the anterior superior iliac spine

The lower insertion is the medial line on the shaft of the tibia

Actions are usually associated with sitting cross legged

Ie it contributes to flexion of the hip and knee, lateral rotation and

abduction of the thigh

Summarized by saying that it paces the heel on the medial side of

the knee

Note: the other anterior muscles (excluding sartorious) make up the quads

Rectus femoris:

This is a spindle shaped bipennate muscle, it seems to stand out on the front of the

thigh

It is the at the very middle, front of the thigh, superficial, and just medial of the

vastus lateralis

Its upper attachment is two heads which are continuous, one to the anterior inferior

iliac spine, the other to and area above the acetabulum

The lower insertion is at the upper border of the patella

The actions are hip flexion and knee extension

Vastus lateralis:

This is situated on the anterolateral aspect of the thigh, lateral to the rectus femoris

(ie the outside of the thigh)

The upper attachment is the intertrochanteric line

It also attaches to the fascia lata

From this origin the fibres run downwards and forwards

The lower insertion is the tibial tuberosity

The action is the knee extension

Vastus medialis:

This is situated on the anteromedial aspect of the thigh, medial to the rectus femoris

(ie inside of the thigh)

Its upper attachment is extensive at the intertrochanteric line

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It then runs down around the linea aspera and the upper part of the supracondylar

line

Its upper fibres pass downwards, whilst its lower fibres tend to pass nearly

horizontally laterally

The lower insertion is the tendon of the rectus femoris

The action is the extension of the knee

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Vastus intermedius:

The deepest part of the quadriceps femoris lying between the lateralis and medialis

It is deeper than the rectus femoris

The upper attachment is the upper two thirds of the anterior and lateral surfaces of

the femur

In the middle of thigh it is difficult to separate from the lateralis, whilst at the

bottom difficult to separate from the medialus

The lower insertion is the tibial tuberosity via the tendon of rectus femoris

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The action is extension of the knee

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Posterior group (hamstrings)

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Biceps femoris:

Situated on the posterolateral part of the thigh

Long head: this has an upper attachment at the ischial tuberosity, with the tendon

of semitendinosus

With a posterior view it is in the middle, and fairly superficial and large

The lower insertion is the head of the

fibula

Short head: this attaches to the linea

aspera

The lower insertion is the head of the

fibula

The actions are the extension and

external rotation of hip, and flexion

and external rotation of knee

Semitendinosus:

The upper attachment is the facet of

the ischial tuberosity

The tendon then combines with the long head of the biceps femoris, and the

muscles run together

It then forms a fusiform muscle belly, which gives way to a long thin tendon

It passes downward and medially behind the medial condyle of the femur

This is just lateral of the semimembranosus muscle

The lower attachment is the medial surface of the tibial shaft

The nerve supply is the tibial division of the sciatic nerve

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Actions are extension of hip, flexion and medial rotation of knee

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Semimembranosus:

It is situated on the posterior medial side of the thigh, deeper than the

semitendinosus

The upper attachment is the ischial tuberosity

It then passes downward and medially

It is muscle at the top and a thick flat sheet of

membrane at the bottom

At the bottom it spreads in many directions,

particularly upward forming the oblique popliteal

ligament

The lower attachment is the medial tibial condyle

The actions are extension of hip, flexion and medial

rotation of knee (same as semitendinosus)

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Medial group

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Gracilis:

From posterior view this is the small, long, thin medial

muscle

This is the most superficial muscle of the adductor

group

The upper attachment is the front of the body of the pubis

It develops a fusiform shaped belly at its middle

It becomes tendinous above the knee and crosses the joint

The lower insertion is medial surface of the shaft of the tibia

Its actions are mainly flexion of knee, but also adduction of hip and medial rotation

of thigh (with knee semi flexed)

Pectineus:

This is a quadrilateral muscle situated at the upper and medial part of the thigh

It appears to consist of two layers, superficial and deep, supplied by different nerves

Its upper attachment is the superior ramus of the pubis

Its fibres pass downward and laterally between the psoas major and adductor

longus

Its lower insertion is the pectineal line (line from lesser trochanter to linea aspera)

The action is flexion and adduction of the hip

Adductor magnus:

This is the largest and most posterior of the adductor muscles (lies posterior to

brevis and longus)

It lies anterior to semimembranosus and semitendinosus (is very deep)

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Its upper attachment is the ischiopubic ramus, running down toward the ischial

tuberosity

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The ischiopubic fibres fan out forming a large triangular muscular sheet

These fibres pass laterally and slightly backward toward the linea aspera,

and may be fused with the quadratus femoris

The fibres from the ischiopubic ramus run the length of the linea aspera

The posterior ischial fibres pass downwards and attach to the adductor

tubercle on the medial condyle of the femur

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Action is hip adduction

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Note: be careful as this sometimes may look like part of the hamstrings

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Adductor longus:

This is a long slender, triangular muscle (also very deep)

It is situated on the medial aspect of the this, overlying the middle part of the

adductor magnus

The upper attachment is the obturator crest on the body of the pubis

It passes downward and laterally

The lower attachment is the middle half of the linea aspera

Actions are adduction of the thigh, flexion of extended thigh and extension of flexed

thigh

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Adductor brevis:

This is a triangular muscle situated on the medial aspect of the thigh

Its upper attachment is the inferior ramus of the pubis

Its fibres pass downwards and laterally backwards

Its lower insertion is the upper half of the linea aspera (anterior to the adductor

magnus, and posterior to the adductor longus)

Its action is simply adduction of the thigh

6.2 Using the muscles of the thigh as an example, describe the effect on joint function of

muscles, which cross two joints

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Long muscles act across two joints (ie the hamstrings, rectus femoris)

In this case they can only work efficiently across one joint at one time

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Ie the hamstrings can only extend the hip strongly with the knee in extension

6.3 Describe the functions of the different components of the quadriceps femoris muscle

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Each of the quadriceps femoris has a particular role in a certain range of movement

Rectus femoris: commonly performs the swing phase of walking, when the limb is

carried forward and the knee is being extended

Vastus medialis: in the final stages of the extension of the knee, helps the locking

mechanism of the joint

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Vastus lateralis and intemedius are used for the extension of the knee

6.4 Observe and palpate on a living subject the bellies and / or tendons of the following

muscles of the thigh:

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Rectus femoris:

This can be palpated near the hip on anterior surface of the spine

Externally rotate hip and then resist flexion, a v is formed pointing toward the foot

The space in between the v is called the rectus femoris

Vastus lateralis:

Forms a visible bulge on the lateral side on the knee with isometric contraction

Vastus medialis:

Forms a visible bulge on the medial side of the knee with isometric contraction

Semitendinosus:

With medial rotation, both the gracilis and semitendinosus are prominent

The semitendinosus is the larger of the two and most lateral

Semimembranosus:

Most prominent tendon in the back of the knee on the medial side

Most palpable when the patient is prone or seated and resisting knee flexion

Biceps femoris:

Palpate from common origin on ischium to insertion on lateral side

Most prominent when the patient is prone and resisting knee flexion

Sartorius:

This is most easily palpated at its proximal end, just below the anterior superior iliac

spine

Here the strap like shape can be easily palpated particularly when the knee is slightly

flexed

It is best when the left is raised slightly from the floor when lying in supine

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