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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