Posterior compartment of the

thigh

Dr. Heba Kalbouneh

Associate Professor of Anatomy and Histology

1-Muscles:

Biceps femoris

Semitendinosus

Semimembranosus

Adductor magnus (hamstring part or ischial part)

2- Blood supply:

Branches of profunda femoris artery

3- Nerve supply:

Sciatic nerve

Posterior compartment of the thigh

Biceps femoris

Semitendinosus

Semimembranosus

Hamstring part of

adductor magnus

The posterior thigh muscles were called “hamstrings” because

butchers used to hang pigs by these muscles outside their shops

In ancient times, the soldiers utilized to slash the rear of the knees of horses of their rivals to be

able to cut the tendons of hamstring muscles, to bring the horse and its rider down. They also

utilized to cut the hamstring tendons of soldiers in order that they couldn’t run. This was referred

to as “hamstringing” the enemy.

All Extend the hip EXCEPT short head of biceps

All Flex the knee EXCEPT adductor magnus

Lateral muscles rotate the knee laterally

Medial muscles rotate the knee medially

Ischial tuberosity

Origin:

All from ischial tuberosity EXCEPT

Short head of biceps femoris from

linea aspera and lateral

supracondylar ridge.

Insertion :

Biceps femoris: head of fibula

Semitendinosus: upper part of

medial surface of the tibia (SGS).

Semimembranosus: medial condyle

of the tibia

Adductor Magnus (Ischial head):

Adductor tubercle of femur

Biceps femoris Long head

Biceps femoris Short head

Origin: two heads

1-Long head: ischial tuberosity

2-Short head: linea aspera, lateral

supracondylar ridge

Insertion: Head of fibula

Nerve supply:

Long head: tibial portion of sciatic

nerve

Short head: common fibular portion

of sciatic nerve

Action: Flexes and laterally rotates

leg at knee joint; long head also

extends thigh at hip joint

Biceps femoris

Origin:

Ischial tuberosity

Where?

Insertion:

Upper part of medial surface of shaft

of tibia (SGS area)

Nerve supply: Tibial portion of

sciatic nerve

Action: Flexes and medially rotates

leg at knee joint; extends thigh at hip

joint

Semitendinosus

Semimembranosus

Origin: Ischial tuberosity, where?

Insertion: Medial condyle of tibia

(posterior surface) Groove for semimembranosus

Nerve supply: Tibial portion of sciatic

nerve

Action: Flexes and medially rotates leg

at knee joint; extends thigh at hip joint

Biceps femoris

Anterior

Posterior

Semitendinosus

Semimembranosus

The ischial tuberosity is covered by gluteus maximus when one

stands. In the sitting position the muscle slips away laterally. To

palpate this bony point, therefore, feel for it uncovered by gluteus

maximus in the flexed position of the hip

Ischial tuberosity

Divided by a transverse ridge into:

An upper quadrangular and a lower triangular

parts

The lower triangular part is divided by a

longitudinal ridge into:

1-Lateral part that gives attachment

to the ischial part of the adductor

magnus

2-Medial part (subcutaneous part)

Covered by connective tissue and bursa

The upper quadrangular part is divided by

an oblique ridge into:

1- Upper Lateral part for the attachment

of semimembranousus

2- Lower Medial for the attachment of

semitendinosus and

long head of biceps Medial Lateral

When sitting, this medial part

supports the body weight

Qu

adra

tus

fem

ori

s

Inferior gemellus

Pay attention to the fact that the muscles of the thigh are designed

To act on the knee joint

For example, quadriceps femoris occupies the anterior compartment of the thigh but its

Main action is to extend the knee joint

The same should be considered for the muscles of the posterior compartment of the thigh

Although they occupy the posterior compartment of the thigh

Their main function is to flex the knee joint

Now think!

Which muscles will rotate the knee joint medially and laterally?

Keep in your mind that when the knee joint is extended medial and

lateral rotation is not possible!

The joint said to be locked

Therefore, we need to unlock the extended (locked) knee joint

A small muscle called popliteus unlocks the knee joint by

rotating the femur on the tibia laterally before any flexion of the knee can take place

Now the joint is unlocked

Only now when the knee joint is semiflexed:

The biceps femoris can act as a lateral rotator of the leg

The semimembranousus and semitendinosus can act as medial rotators of the leg

Sciatic nerve A branch of the sacral plexus

(L4 L5 S1 S2 S3)

Emerges from the pelvis through the

greater sciatic foramen below

piriformis

Is the largest nerve in the body

Consists of the tibial and common

fibular nerves bound together with

fascia.

Commonly terminates in the

lower third of the thigh by

dividing into:

Tibial nerve

(Medial popliteal nerve)

Common fibular nerve

(Lateral popliteal nerve or

Common peroneal nerve)

Surface anatomy of sciatic nerve PSIS

Greater trochanter

Ischial

tuberosity

The greater trochanter of the femur

can be felt about one hand’s width

inferior to the midpoint of the iliac

crest

The ischial tuberosity is palpable

just above the gluteal fold

A branch of the sacral

plexus S1,2,3

Enters the gluteal region

through the lower part of the

greater sciatic foramen below

piriformis

Supplies the skin over the

back of thigh and upper part of

the leg

Posterior Cutaneous Nerve of the Thigh